I'm about to install a GM Goodwrench ZZ4-350 Crate engine into my 1977 Base Firebird but, I need to know if I would have to replace the 3 Speed Automatic Transmission with a new one with overdrive. Does anyone know if replacing the transmission is mandatory ?, and would a 700R4 be a good choice for a replacement ? Thanks

I can't think of a reason it would be mandatory, but with gas prices what they are I'd think about it. Might be easier to live with on the highway as well. Nice choice on the ZZ4 also

If your 77 Firebird has a Pontiac motor in it,the transmission will not bolt up. If it has a pontiac motor you really should try to keep it that way.

It does have a motor in it, its got the 1977 Pontiac Base Firebird (5.0L 2BL OHV) VIN code U. The problem with the engine is just the carburetor is shot so I thought I would finally just tune it up really powerful, but I could just replace the carburetor to keep the genuine motor but, I would still like a little more horsepower, any suggestions on new carburetors, engine boring, or air Intake types? I'm open to all improvment suggestion. Thanks

Good point, had not thought of that.