Starting this thread to show my project upgrading my '68 Cutlass Holiday coupe factory front bench / lap belt combo to a safer buckets (w/ headrests) and 3-point belt arrangement. One of the primary drivers of this is my planned future engine rebuild that will have LT headers, so I also need to eliminate the column-shift mechanism and replace it with a floor shifter. I've determined that with the bench in its most forward position it will force placement of the floor shifter too far forward, and I have no desire to customize my bench to notch-out the center for additional shifter clearance as I've seen done elsewhere here. Also, instead of factory-like bucket seats, I'm going aftermarket to get some additional side bolstering since part of my plans include a significant front suspension / wheel upgrade to vastly improve max cornering forces. So I'm going with SCAT/ProCar Rally 1000 seats and their appropriate adapters to fit them to the factory bucket mounting locations (P/Ns 80-1000-51L/R):



Adapter bracket PNs are 81504 & 81505:


Of course, since I have to add the inboard bucket mounting points, I picked up a set of conversion brackets:


For the seatbelts, I'm using a set from Morris Classic Concepts PN MCSB1-9-BK:


For the shifter, I picked up a Hurst V-Matic 3 that works w/ my 200-4R (installation of this will not be the focus of this thread).

More to come.

 

TOOLS: While I learned to weld (MIG) back in '86 when I was doing some body panel patches prior to it's repaint, I am still a novice since I've had no experience welding since then. Since the conversion brackets are welded to the floor pan, I planned to use a cheap flux core wire feed welder that I picked up from "that place". It turned out to be pretty decent for the barely over $100 price and it even came with a spool of wire and an auto-dimming helmet. All I needed was to pick up some leather welding gloves from the local H/F and I was ready to learn again.

 

Here's my starting point after the old bench and belts have been removed:


So the plan was to use the ProCar adapter brackets to locate the new bucket conversion floor brackets on the floor pan:


Seems straight forward. Bolt the bucket conversion bracket to the seat adapter brackets, bolt it to the outboard mounting points and mark where the inboard conversion bracket touches the floor, then weld away. However, a couple of issues I ran into was that the conversion brackets' studs were just a tad too far apart to fit the seat adapter bracket. I started just elongating the two inboard holes on the seat adapter brackets, but after doing that and "hammer forming" the conversion brackets to the floor contour, the two studs splayed-apart enough to no longer fit the seat adapter bracket holes. At this point, it was just as easy to cut the ends off the conversion brackets and center the mounting studs in the holes of the seat adapter brackets (to maximize location margins) and locate it that way. It also became apparent that I was going to need to shim-up the inboard rear location to keep the seat adapter bracket square to avoid issues when mounting the seat to them:



After farting around with this, I was able to get the ends of the conversion brackets welded to the floor pan in the proper location (only burnt-through the floor twice, and while my beads aren't pretty, I got enough good beads around the perimeter that I'm confident they are plenty strong).




(Those washers are the shims used at the rear inboard mounting location to avoid twisting the adapter brackets)

Adding 4 more flaps to the carpet and it was ready to mount the adapter brackets to the floor.

 

After assembly of the slider mechanism to the seat bottoms, the seats were then attached to the adapter brackets.


The slider mechanism provides 3 mounting slots for this to allow adjustment of the height of the seat from the floor. For some reason the passenger side was too low to the floor pan to allow use of any position but the highest position on the rear side.


On the driver's side, I was able to use the middle slots front and rear. So my plan is to remove the passenger side seat and cut-off the bottom of the slider bracket on the rear to allow use of the middle slot.

 

Once the seats were mounted, I noticed that the driver's side is centered ~0.5 to 1.0" to the left of the C/L of the steering wheel, barely noticeable. Also the seats were equidistant from the door panels indicating that there is decent symmetry in the locations of the seats (thank goodness). However, with the seats forward and/or seat backs too far forward, the seatback side bolsters would press against the interior door handles when closed, compressing the foam cushions in each a tad. But after adjusting the driver's seat to a comfortable position (for me), the side bolster shifted rearward enough to avoid this interference. Same situation on the passenger side after adjustment. I'm estimating ~3/4" interference between the door handle and the seatback side bolster (these next 2 photos are shown with the seat far enough back so that there is no interference):


For short folks or more rear legroom, this interference could, IMO over time, result in wear on one or both parts, especially if adjusting while the door was closed. I'm going to get into the habit of having passengers adjust their seat before closing the door to mostly avoid this (but will likely still semi-permanently compress the foam).

When its all said and done, those front seat positions leave only ~6" between the front of the rear seats and the back of the front seats.


There's a generous 11" between the front seats, leaving at least 9" of width for a custom console (and allowing 1" each side for the inboard seat belt).

 

ProCar does offer a Pro-90 series seat that has a headrest and much less aggressive (nearly non-existent) side bolstering that might eliminate the door handle interference issue, but I've already walked off that plank.


I should also point out that the side bolstering does constrain the room for getting in and out of these seats (especially the driver's side). Also, I'm ~185 lbs and 5'11" and the Rally 1000 seats are snug, so wider folks should probably avoid the Rally 1000s and go with the Pro-90s instead.

 

Working on mounting shifter, then will post again when seatbelts are installed.

LMK if any questions, feedback welcome.
................

 

I got my shoulder Belts from Morris. I liked the quality and went in fairly easily.

 

Good feedback, I was hoping these were good. Not the cheapest, but looked good quality and had the configuration I wanted. Thanks.

One other thing I should mention about the Rally 1000 seats is that the side bolsters do limit how far forward the seat can be folded tilted to get into the back seats. The backs will go about vertical (from a laid-back position) before the side bolsters limit motion. I'll likely find that the seat bottoms will also need to be slid as far forward as possible.

 

Completed the shifter install (cleaned up the "fire hazards" lurking under my dash while I was at it), still need to install the belts.


What to do with the old column shifter? No plans of swapping the column. Hopefully its just a roll-pin push to pull the handle. Maybe leaving it as-is will confuse potential thieves, lol.

On the other hand, if I stumble across a floor-shift tilt column I'm going to nab it. That big wheel becomes an obstacle getting in/out over the seat bolsters.

 

A quick release steering wheel mount will cure some in/out issues, and bonus hard to joyride a car with no wheel.
Nice write up. I'll have to look if the seats come in cloth.

 

Thanks, and that's not a bad idea. I do think that the ProCar seats are available in different colors and materials (I haven't dug into the selection deep enough to remember specifics).

I did get the belts installed, need to pull the photos off my phone and complete the write-up.

Well, it already confused it's owner. Yesterday I took my son to his doctor's appointment in it, and when backing it out of the driveway I instinctively grabbed the column shift handle. ​​​​​​​

 

Belts Installation:

Since my car wasn't built w/ shoulder straps that were optional at the time, I had to locate the mounting points for the shoulder anchors. This shows that location WRT the front edge of the rear window (fully rolled-up) and the garment hanger:


If you press on the headliner in this area you can feel the two holes for the anchor mount. Trimming out two small holes there reveals the screw holes:



I recommend mounting this shoulder anchor first, which helps keep the belts from twisting between this and the floor anchor assembly (on the first side I did, I had to disassemble the floor anchor retractor from the lap belt bracket to untwist the belts before mounting them to the floor). I also found that when the floor anchor retractor was mounted and aligned with the shoulder anchor (to prevent the belt from rubbing on the retractor housing) that the retractor housing rubbed up against the cover for the seat reclining mechanism:



So I took it apart and bent the right-angle bracket that ties the retractor and lap belt bracket to the floor to gain some clearance:



The last step was to mount the inboard belts. All new floor anchoring hardware was included with the belts:


(I will eventually install a console to prevent these from flopping over each other and keep them in position where they need to be for easy access).

Here's a shot of the passenger side final installation, showing that if the seat is moved forward and tilted forward (and pull the belts out of the way) that access to the rear seat isn't bad at all, just more moving parts than for the old bench.



About the only tweak left to do is to somehow add a guide to the top of the seat near the headrest to make it easier to reach the belt when seated, its a far reach back over the shoulder to grab the belt. It isn't ideal like B-pilar mounted shoulder anchors like modern cars have, but I think it is an improvement over the dual shoulder + lap belts (and two buckles) factory setup.

Let me know if there's questions or some detail I missed. Thanks for following along.

 

Looking great John.

 

Thanks Matt!

 

I searched for a 3D model for a seat belt guide and found a couple for Triumphs and MGs, but nothing that looked like it would work for me and didn't require a bunch of supports when printing.. So I decided to use the (very basic) MS-3D Builder that comes with Windows to create my own design. After a few iterations to evolve the design into something both functional and not in the way, I came up with this design. In order to be located by both headrest posts, it ended up longer than would fit my Ender 3 (220x220mm). So I split it in half and added some locating cones in the joint that also improve strength when the two ends are epoxied together.

It isn't perfect, the 3D Builder left some strange, barely visible artifacts on angled surfaces that were "milled" down during model build. I'm sure someone more fluent in mechanical CAD could clean this up quite nicely (being a retired EE, the only CAD I needed to learn was electrical schematic capture, PWB layout and circuit modeling).




Using black silk PLA and only 10% fill when slicing, the resulting part is surprisingly strong. If it ever breaks, the infill can be increased to make it stronger. Also, if I ever do have to print this again, I'll probably use some matte finish black filament instead of silk, which has a brownish hue next to the black vinyl of the seats.




I've attached the STL file that can be used for 3D printing. As mentioned, 3D Builder seems to struggle with angled surfaces, but it was easy enough for me to learn so that's what I used. As such, I've had no problem dropping the STL file into my slicer, but when importing it back into 3D Builder it gets flagged as "needs repair" and if selected, 3D Builder stalls during the "repair" and doesn't finish the process. Not sure what's up with that.