6 or 12 volts?

[Vanspeed]

I recently picked up a 48 f-1. It is an all original truck. Last owner cobbled up some wiring and has a 12 volt in it. I want everything to work on this truck, heater, gauges, etc. it is only wired to run off the 12 volt. Should I go back to 6 volt? I want to re-wire the truck with original style wire harnesses. I down care about dimmer lights as this isn't going to be driven at night that much. Mainly Sunday lumber yard runs and general farm use.