The 700r4 will handle that kind of weight just fine. Use a large cooler, stay out of OD except for long flat roads and I would recommend a beefier 3-4 clutch pack kit. It sounds heavy but realize the rearend is geared twice as low as most 3/4 tons. So that takes a lot of stress of the power train.
I slammed a 6.2 Diesel and 700r4 Into a 54 GMC M211 Deuce. It had banjo 6.17 axles too. Do use a later 700r4, fewer issues. I believe mine was from a 1991 s10.
