When I changed my truck over to 12 volts I installed reflector assemblies that look identical to the sealed beams and take an H4 bulb. They are 60 watts on low beam and they perform like a much more modern vehicle. You can get them in a six volt 60 watt version but you would want to use relays to power them. I bought mine from Octane lighting. I believe Chevs of the 40s sells a version too.
