Most (maybe all) 6V generators have a short, straight housing with a spring steel band around the brush area. The average 12 volt unit has a longer, stepped-down housing without a band. I don't recall that kind of difference in starters.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!