Well the 8LHP90 will take more torque, I think the factory rates it at 849 ft. lbs., more gears equal better acceleration, and better mileage, of the 2 autos you listed, both would need a stand alone computer to work. The T-56 will work nicely, and now they have one with the shifter at the very end of the tail-shaft housing. However, you will be doing some serious fabrication work to install any of these transmissions. I installed a viper t-56 into my car, had to rebuild entire tunnel and torsion bar cross-member, dropped my motor mounts an 1" to help get a better driveline angle (nothing hangs below frame rails amazingly), oh and when it was all said and done realized that if I want to run an aluminum drive shaft that will take the power I am making w/o me worrying about it, I need to step up to a 3.5 shaft (I could run a steel shaft in 3" and be just fine but...). The rest of the tunnel is too small to run a 3.5 shaft, because at full suspension compression it will hit. So now I will have to section the rest of it and make it 1" taller. Not incredibly hard but very involved. I would say do your homework, and know that you will probably hit some hiccups along the way, and you may have to make some sacrifices. Part of the reason I did mine the way I have is I wanted to keep factory A/C heater box which is huge. So that meant I couldn't run the tunnel as high as I would've liked. In retrospect, I should've said to hell with it, sold it, and got vintage air which is considerably smaller, and redone the entire tunnel... would've been easier in the long haul.
