If there is a metal tag on the starter, a 6V unit will have black paint. A 12V is red. Ditto on the shaft size difference, but I'm not at my shop right now to provide any measurements.
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!