The '37 has a voltage cutout instead of a voltage regulator. If you are going to retain the original voltage cutout, I believe you will need to use the original headlight switch which includes a setting that boosts the generator output so that headlights and options such as a heater or radio don't run the battery down.The switch includes a resistor for when there is no load other than the ignitions system, so that you don't overcharge the battery. This is my understanding of the original system which my '37 retains. I have been told this system is the same as old tractors. I kind of like it as you have to think about what your electric system is doing and watch the ammeter while driving. A little less automatic than when using a voltage regulator. I only have a heater in it so it is no big deal.

If you want a copy of the original wiring system I can send you a photo (too big to fit in my scanner) that came with my harness from Rhode Island Wiring.

Regards,
Kent

1937 Chevy 1/2 ton
1942 Chevy 1/2 ton
1947 Diamond T Model 509
1951 Chevy 1/2 ton
1950 Chevy COE Model 5700 ~ "Barney" ~ And more pix