The Montana uses the 4T65E...
The 4T65E-HD is in the pontiac grand prix and with reinforcement is handling upwards of 400 hp.
For performance parts for this tranny (the 4T65E and 4T65E-HD) check out
http://www.intense-racing.com/
They sell an upgrade kit but you're better off just starting out with an HD given the price
D
slightly
modified 2000 Grand Prix
2000 Pontiac Montana