actually JD, the 6V starter will not only be fine for ages on 12V as long as you don't try to move the truck around the yard on it, but it'll spin over way better than a 12V one .... you will need the 12V gen/reg tho, and of course the proper resistors on electrical gauges .... and don't waste yer cash on "ordering" anything until you try to find good used, there's no doubt a few 12V generators lurking in folks stashes here, find one cheap and put in new brushes
Bill