for the transmission front....stock T5 will hold up, but its hit or miss and depends 100% on your driving style...I had a customer at the shop I worked at, with stock T5 in his full weight 94 GT ragtop, R302 blocked 331 stroker, custom cam, Vic Jr Heads, Vic 5.0 intake, Vortech S-trim that was pullied to the max with a Snow Performance meth kit, Centreforce DF clutch, STOCK T5, and Stock rear end save for 3.73 gears....on a 17inch MT Drag radial he went 11.60s @ around 125mph, driving like a granny (he walked it out of the hole and got into it)....
Like I said, Hit or miss....depends on how much you want to spend and how fast you want to go for the need to upgrade the transmission to a Tremec or G-Force.... and very importantly your personal driving style.....
IMO, if you're going to make over 600rwhp, then an Auto is a good stepup....some of these cars can get pretty violent to drive on the street...which then requires crazy expensive clutch setups like a McLeod Twin Disc or Spec Stage 5s etc etc...
I mean for the price of a heavy duty Tremec or T56, and the price of a clutch like a McLeod or even the Ram twin disc, its almost the same price for a well built AOD .......