I believe Crown sold a conversion kit to beef up the original Corvair 4 speed transaxle, which was flipped over or modified in some way to bring the power input in from the front of the box. My memory of exactly how the conversion was done is a little bit fuzzy after 40-something years. I do remember that the axle shafts from the transaxle to the rear hubs were considerably bigger than original!
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!