4L80E and a standalone controller like optishift.
Programmable, gives you "paddleshifter" capabilities, etc.
Get a 4L80e built 99+ and you get the solid input shaft.
Damned near impossible to break a stock 4L80E at the figures you've quoted.
Build it a little bit and they're total monsters.
Problem with the 60 is it relies on bands for engagement. The 80 is a clutch pack style transmission.
But with that beef comes mass. IE: it's bigger, it's heavier and it gobbles up a little bit more power in parasitic/drivetrain losses.
Or, you could go with a manual trans and gain strength as well as a small bump in MPG....
*edit - Oopps. It appears "optishift is now "USShift" -
http://www.usshift.com/ made by the same company though, Baumann