I finally got around to adding relays to my headlights. It was going to be an "off season" project but the wife and I still love running the 67 in the fall, even though it's getting dark quicker, so I thought I might as well knock it out.

I can't take credit for the photo below. I took a screen shot off of a video and added my notes for my project.


These are the before photos -



And these are the After photos -



The before and after photos were taken with the engine off.
(Don't mind the wires in the "after" photos, I took care of those after I made sure everything was working properly.)

 

Looks like you made a significant improvement in getting the juice to the bulbs. I noticed that the headlights on my 72 look much like your Before pics. I carefully cleaned the bulb barbs and connector brass, it didn’t make much of an improvement. So if I have a wiring/connector corrosion or oxidation problem it is somewhere else. Where did you mount the relay?

 

Correct. There is minimal voltage drop at the lights now.
Have you checked your grounds?
I haven't mounted the relays yet. For now, they are behind the battery, laying on the inner fender. This off season, I am pulling the motor and detailing the engine bay. That's when I'll permanently mount the relays

 

I am going through engine bay as well, but not removing engine. So as I get to any ground connection point I am cleaning them up. I would have to go look and see where the headlight grounds are? Surgery anesthesia is making my mind a little sketchy and don’t recall? I didn’t think of doing it, but I could do a voltage reading at the headlight connectors to see what they show. Maybe even a headlight switch issue? 53 years old now.

 

That's what I did, I took voltage readings at the lights.
On the 67, two headlights share one (small ga) ground wire.

 

Here's the voltage drop (in percent). This is comparing (non running engine) voltage to the voltage at the lights.
Before adding relays
Low Beams - 7.8%
High Beams - 14%

After adding relays
Low Beams - 0.8%
High Beams - 5%

 

The high beam switch is a choke point. You effectively end up with a series switch situation, which is 2 mechanical connections. I'm a big fan of eliminating load from switches, even with the added points of failure.
Frod used standard 5 pin relays for fuel pumps in the 80s, so most parts stores stock them. I'd venture they're more readily than a floor mount, high beam switch from the 60s.
I'm in that dilemma right now. I like having available parts, but the waterproofing and packaging are obstacles. I think I have settled on the MSD SSRs in 4x35a configuration. 1 for fans, 1 for lights under the hood and 1 inside with 1 spare.

 

I put a spare relay in the glove box right away. Just in case.