AaronW,
The primary issue with 6 volts is that for a given job to do, for example headlights, it requires twice the current. By design the 6 volts lights are every bit as bright. But over time, as corrosion creeps into connections and the switch, resistance builds up and the lights dim. Or the starter doesn't spin like it used to.
The other issue is accessories, like a modern am/fm radio or aftermarket wipers, all which may require 12 volts.
I like to try to stay original and am quite satisfied with my trucks that are 6 volts. When I restored my '50 COE I was surprised how bright the 6 volt headlights were (and still are 6 years later). I do not, however, use any of my trucks as a daily driver. If you are having dim headlights, difficulty with warm starts (starter is not spinning) I would try first to go through and clean connections, grounds, etc. If you are not having problems and don't need a modern stereo system or air conditioning leave your system alone. Six volt items like bulbs, voltage regulator, coils, etc are not hard to find through the old truck vendors linked on this site.
Kent
