There's a lot more brains and experience out there than I would ever claim to have. On the other hand, I do know Foyt pulled it off. Not sure how as the old Hot Rod Magazine article is long gone. So, how did he do it? A boat motor with reverse rotation would work. Weakened old guy memory says that was it. Getting a reverse set of ring and pinion would work. I know for sure it worked. Believe Bill France caught him at it. Remember, the term banjo comes from the old style of rear unit manufacture where the carrier assembly as a separate unit. W/o the carrier and the cover the casting looked like a banjo. You could flip the carrier assy and axles and it would work - in reverse This would be fun to pursue. Sorry for the false lead though.