The difference is in the diameter of the flywheel/flex plate. I don't recall which is which, but offsetting the starter drive gear aligns it with the different flywheel diameter. The dimension change isn't much, but it's important to match the starter with the flywheel.
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!