Hi Little Jo,
I bought a Ford GPW jeep last fall that had already been converted to 12 volts with an alternator fitted.The jeep sure starts nice but have not driven it much yet.One positive thing going to 12 volts is the fact that the headlights in 6 volt are drying up from what I have been told but the 12 volt ones are still available and reasonably priced.Here are some pictures of what I have in my jeep if it helps in any way;
I am glad you brought up this subject as I have to figure out myself what to do with the fuel guage to make it work on 12 volt system and anything else that has to be converted.
Regards,Derk.