There wouldn't be a need for a relay, since if you use the original 6V wiring, it'll probably be larger gauge than a newer 12V harness. Smaller wire increases voltage drop, and would be the only reason you'd need a relay for the headlights, which reduces voltage drop thru the switch contacts (actually eliminates the switch in the actual light circuit).

Theoretically your voltage reducer should work anywhere in the circuit.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.