The NAG-1 Getrag built automatic transmission.
Coupled with a proper ration rear axle, it can take the torque, stock configuration, and the gearing ... the gearing isnt bad at all:
1st Gear - 3.59:1
2nd Gear - 2.19:1
3rd Gear - 1.41:1
4th Gear - 1.00:1
5th gear - 0 .83:1
Reverse - 3.16:1
And...