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Well, here's what WE found, FWIW. Rewiring this little '37 Coupe from scratch recently, 6v, STOCK STOCK. I bought this coupe 20+ years ago, stock as could be, really nice un-restored condition. Well, I let it sit all this time and recently decided to sell-out all my junk for health reasons. My best bud did all of this work to get the car running, safe and reliable for his brother in NW Ohio who bought the car.
So, my bud got the car running and stopping well again (stock cable brakes). With that, he completely rewired the car using all reproduction wiring harnesses. As found, none of the lights were even wired-up. The passenger side headlight reflector was some sort of reproduction....didn't even have the hole for the park light socket.
I found two solid, yet tarnished-looking reflectors on eBay for $20. They ended-up polishing-up very nicely.
Note in the first picture the black Yuckelberries all around the big hole for the bulb and socket. I'm gonna assume that is possibly some carbon from arcing of a loose bulb and socket over the years. More importantly, THAT IS YOUR GROUND surface. Long story short, that was all easily cleaned-up, and a ground wire soldered to each of a pair of NICE, stock bulb sockets from a '39.
Think about that GROUNDING situation ...bulb/socket assembly grounds to reflector. Reflector grounds to bucket. Bucket grounds to fender. Fender grounds to body, and grill assy at front, which all eventually grounds to chassis. We ran the soldered ground wire down with the stock harness to a point where each side's ground wire could be grounded through an empty, stock hole in the chassis on each side. Third picture tells the story on that.
One thing to remember on '37-ish headlights is that those flutes in the glass headlight cover are there to aim a stock bulb mounted at a pre-determined distance from the glass. That distance may be compromised when using different type bulbs mounted in different reflectors. In other words, you may have a bright light...aiming toward your bumper. DD