My 1968 442 has been sitting for a few years after a shop bunged up an engine replacement. I'm jump starting that project...

The under hood wiring is a mess. Cut and spliced wires, jumpers taped in, one wire with melted insulation, etc.

I have a 10si alternator so the original regulator is long gone, and I have the pertronix ignition replacing the stock points.

I'm considering replacing the entire harness. How big a job is that? Is there a vendor that makes a good replacement?

 

I hear good things about M&H for factory style replacement harneses. If you want to do an aftermarket, I suggest an American Autowire kit. You will have to enlarge the hole for the bulkhead. Done correctly, you're looking at about a week or $2,000 labor, and that's headlights to taillights. I'm in Central Maryland, and love playing with wires.

 

You can get replacement aftermarket wiring harnesses. Here's one I found with a quick search.

https://www.summitracing.com/parts/sum-rp21505

If you have the skill to install an aftermarket wiring harness it would probably take less effort to repair the existing wiring harness.

 

If it's just the engine harness, it's a fairly simple job. It basically plugs into the firewall bulkhead connector and then you just route the wiring to its destinations and connect. Same with the forward light harness. I would go directly to M&H.

M&H Electric Fabricators
Reproduction Electrical Products for American Muscle Cars

An example from Fusick, don't know who makes it
front engine harness, 1968 Cutlass wth A/C

 

Engine and front light harness both should take less than an hour to install.

 

I replaced the underhood harnesses on my 70 442 with M&H harnesses and it was dead simple. There is a bolt under the hood that holds the harnesses to the fuse block. Remove the bolt and you can unplug the harnesses.
They can put together a harness for you that is setup for whatever alternator that you want to run.

Just be aware that the 58 year old fuse block may not be in the best condition and you might need to attend to the interior harness as well.

Link to M&H wiring: https://wiringharness.com/ymm-search...carline_id=113

 

If you're reasonably methodical in your disassembly effort, you can replace the dash, engine and forward light harnesses in a weekend.

Much of the dash harness may be accessible from the front panel once gauges are removed - at least that's how it was for my '72. Just label your connections as you unplug them to match up with the new harness going in. M&H and I believe American Autowire make factory repro harnesses for plug & play install - available directly and thru vendors like OPGI, Year One, etc.

 

A factory replacement is straightforward.
I believe American Autowire offers terminated and unterminated versions. Making all the ends is the time consuming part.