With the torque that powertrain setup will have available, the obvious choice is a 9" Ford axle- - - -the same basic gearset the NASCAR guys use. Try one from a 1970's Econoline 150 van for approximately the right tread width. There's a trainload of specialty parts and pieces for that axle- - - -limited slip carriers, disc brakes, etc. and any gear ratio you can dream up, also.
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!