I've ruled out a t56 because even the wrecking yards want $1100+ for one with 100,000 miles. So now i'm once again looking at the tko500 or the tko600.
The only real difference between the two is the gearing.
TKO500 3.27, 1.97, 1.43, 1.00, 0.68, 3.00
TKO600 2.87, 1.89, 1.28, 1.00...