Another way to figure out which starter he needs is to measure the size of the armature shaft on the one that's removed, or look at the Delco part number tag if it's still attached. 12 volt starters have approximately a 1/2" diameter shaft and a red-painted tag. 6V units have a shaft about 5/8" in diameter and a black painted tag. Both starters have the same number of teeth on the drive pinion (9, I believe) but the tooth shape and root circle is different. The 12V stomp switch will also have a small electrical terminal for a bypass wire built into the side of the switch.
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!