Going to 12 volt negative ground is a good idea. The started will work, get a 1 wire alternator re worked to charge off idle. Either change the gauges or get dropping resistors. Change the coil and bulbs and be sure you have plenty of grounds. As mentioned earlier 6 volt wiring is heaver gauge because 6 volt runs more current. The heavier wiring is a good idea. I have seen 12volt battery cables get hot and smoke on a 6 volt system. But the main reason to change is because most shops don't know how to deal with 6 volt positive ground systems.So just remove all the wiring and start from scratch with 12 volt negative ground..
