I am lookin to pick up an 89 IROC wiht a 305 and the five speed and want to drop in the GM performance 350 HO. It makes 330 HP and 380 Torque with a carb and headers but i would use the TPI system and want to know if the tranny can handle it, otherwise what can i do, or should i just look for an auto?

It will hold it for a while. I would say after a little abuse and it will go....Mbuddy has a 300horse 300 ftlb in his and the T5 blew up after a while. You have alot more power and torque. I would say that it would break after a year or so. It also depends on if you abuse it alot too. It will hold but under alto of abuse it will die.

Over 115k miles on the clock and I beat it pretty hard at the track and have yet had the first problem. Key is no powershifting(let off the gas in b/w shifts) and no clutch dropping on sticky tires.

Torque is what kills a transmission, not horsepower. As a driver you have some controll over the torque. Don't lauch hard or power shift and it will last a while. But if you ask me, that takes all of the fun out of driving a car.

if you wanna keep the manual go look in junk yards for an 82 camaro or firebird. those had the saginaw 4 speed manual. a much better trany over the 5 speed

127,000 + miles and still tickin'. Never run slicks. The T-5 has handled the 418 lbs I got on motor (not including the NX kit) for over a year now. It needs synchros BAD. But it pulled a 1.9 60' on 255-50-16 street tires. Not bad for OEM.

The t-5 sucks. I have it in my iroc and I have 335 HP and Somethin like 390 tq. My t-5 has been rebuilt 3 times. For some reason 3rd gear blows up. So since Ive had it I dont power shift and dont drop the clutch.
Go with a mucie m-20 or a t-10 4 speeed.

I installed a 300HP crate 350 in my 92 RS last year, and so far the T5 is holding up, but I've been careful not to bang second gear(that's what blew it up last time with the 305).It'll last if you don't abuse it.......but what fun is that?
I'm planning on a Tremec TKO later this year.
-Rich-

Mine is holding up just fine so far. However your bigger problem will be the heads. The 330 HP engine uses the Vortec heads. You'll need the Scoggin Dickey TPI intake. And plan on replacing the transmission soon.