lots of choices here..the 700 R has a low first gear..I believe 3.05-1..correct me if wrong and the forth gear is an overdrive I believe either .86 or .73...for your build up I would go for a 12 bolt with end axle retainers...for suspension you could go for a single leaf,coil over with Cal-tracs......coil over 4-link....as far as the ratio goes a 3.55 with Posi would be good....