Some follow up questions for you:

What car is this going into (how heavy)?
How much power/tq will you be putting down?
What are you looking to do with it? (street, street/strip, full-on race?)

I know many of the big dog door cars at the track (9's and faster in the 1/4) are running Powerglides but I think the TH-400 is a great unit for street, street/strip and most "slower" race-only cars...

Two more cents,

-Chris