I have installed a NOS set of Guide amber fog lights on my 54 3104. They have the 6v composite bulbs. I used an 8amp reducer from the battery to the switch and when the circuit is closed you could boil water on the ceramic resistor in a few seconds. I don't believe there were 12v bulbs for these lights.

How can I reduce the voltage without heating the garage?

Thanks

My rule of life: You can have anything you want; you just can't have everything you want.