I was wondering if I would need to replace or fix my transmission if I threw in a 400 in my 91 Firebird. I heard that if I kept my old transmission, I could wreck it driving the new and more powerful 400. CAN ANYONE VERIFY THIS? PLEASE HELP!

Being as these transmissions were designed to be used in our cars using the stock engines, which put out no more than like 250HP and 350 ft. lbs of torque with the 350 at the most, I would imagine that with the power that a 400 puts out, you will definitely have to do some beefing up of the transmission if you want it to last for a while IMO. It'll bolt up fine and would probably work for a while, but it wouldn't hold up very long I wouldn't think.

But lets hear what others have to say as well

all your questions, even the ones you don't know you'll ask yet, are in the Poncho swap sticky

Plus, it isn't a "Pontiac 305". It's a small block Chevy.