Here's my two cents. If you aren't going to run radios ot other 12V items the 6V system will work fine. Clean all contacts and have good grounds. However, if you want a authentic military conversion you will need to change the following: generator, all lamps, fuel guage, regulator, coil, all pulleys ( 12V uses bigger pulleys ), ant the battery gets relocated in a rack between the seats. The rack holds two 6V batteries, but I use an Optima 12V which will be upgraded to 2 Optima 12V batteries. Radios take a toll on batteries
The one lamp that stays 6V is the fender blackout drive lamp. It gets a resistor that is mounted n the firewall. If you would like I can email you some more detailed photos of what is needed. Don' t forget to get the manual for the conversion. MWO ORD G503-W7 which is available at Army Jeep Parts.
Here is what the generator looks like ( and why the battery no longer fits under the hood.