Just another thought here.
A local guy here where I live, rebuilds starters, alternators and generators and so forth. I took my Farmall Cub tractor's starter to him last summer to have him rebuild it and I was asking him what he was doing for us guys who are running 12 volts on a 6 volt starter.
His response is the same as everyone here, that the 6 volt starter will handle the extra 6 volts with no problem, just not keep grinding on the motor.
Well anyhow, he said that he worked on a older vehicle's starter that kept knocking the teeth off of the drive bendix. So he went to his parts supplier and was looking on what might help keep from doing this. Well what he found was a company that made 12 volt fields for that could be used with the 6 volt starters, what this did was lessened the hard engagement force and faster spinning of the starter motor. He said that the fields run about 12 bucks a piece.
He also told me that since he put these new 12 volt fields in this guys starter, he hasn't had any problems since. I thought COOL, now that I have several teeth missing on my flywheel ring now. Maybe this might been been what happened to mine in the first place. I know when I engage the foot starter that engine is really cranking over quite fast. But my engine starts so quick and easy, that I don't hardly have enough time to get my foot off the starter pedal.
I don't know if this may be a problem with every 6 volt starter running on 12 volts or not, but I thought it was something to think about. I don't feel there would be any problem going back to the original 6 volt system on my truck, but it sure it nice to be able to go to even go, let's say Wal-Mart and buy light bulbs in 12 volts for my old truck. Where I would probably have to order 6 volt bulbs, flasher relay and so forth from a parts store and wait a couple of days to get em. For that reason alone, and since it's a semi-daily driver, I really like having the 12 volt system on my old 54.
EVEN THOUGH, I was surprised the other day when I went to one of the parts store and they actually had a new brake light switch for my truck, on the shelf. They pulled out a couple different styles and the one was the correct one for my truck...... better yet is was only 12 bucks and even more surprising, is was MADE IN U.S.A. I about fell over.