I have a 305 right now in my 92 firebird and i was looking to put a 350 in there. My question is if i swap it do i need to change the ECM and the PROM? I know that the PROM is for the 305. So do i just need a PROM or a whole new ECM. And if i get a new ECM will it hook up to the wiring harness in my car now?

I'm going to be doing a 305 to 350 swap in the very near future also. i've got some info from a friend of mine, he says the ecm should be fine, but he thinks i'll need to change the EST control and possibly bigger jets because i'm running a carb. i doubt it would hurt if you got an ecm for a 350 car and put it in. i just came on here to verify all that (per his suggestion, he wasn't completely sure) and find out if there's anything else that won't be able to swap over. hope that helps a little.

So you are saying i should be ok and wouldnt have to change the computer or the chip from my 305 and it would be able to work for my 350?

according to all the info i've gotten so far, it will run fine if you keep the 305 ECM and PROM. Although you may run into fueling issues when you get on it with the 305 PROM. unless it's necessary for you to keep the 305 PROM due to cash issues or whatever, then i would change it.

i'll be changing mine, a friend offered to burn me a copy of the ZZ4 chip for my new engine. but i'll probably end up running the 305 PROM for the first couple weeks or so, until the motor is broken in.

also you may want to look into the knock sensor, if the engine you get doesn't have one , you won't be able to use the one from the 305.

What will you be running for induction, carb or tpi ?