Those are great looking cars and pretty scarce these days. It is extremely easy to get so much power and weight up front that traction is non existent. The LS options or a reasonably mild 350 will make a great nice to drive vehicle. If you lean toward more originality or an early Transam tribute, then maybe Pontiac power could be interesting. I tend to like builds that have a chance of being worth as much or more than I have in them myself and I can actually drive comfortably without running hot or other issues.I just ended up with a 1969 Firebird roller and I'm debating what engine to put in it.
I have a built 454, ~550 HP, and built TH400 that I was planning to put in a '57 Bel Air. Downside of using this for the Firebird project is that I have ceramic coated headers specifically for a BBC in a Tri Five, so I'd have to sell those.
I have a SBC 400 block and all the parts I need to build it except rotating assembly.
I have a tall deck 427 block but no parts for it.
I have a friend of a friend with a 1980 Firebird that has been parked since 1989, with a built Pontiac 400 and TH400, and headers, that I think would fit the '69 Firebird, that he would sell for $2000. I could also probably use the front seats and then sell what's left. The paint is ruined from sitting under pine trees and of course engine and transmission would need fresh gaskets at minimum.
I saw a recently rebuilt Pontiac 400 engine, complete with headers, but no intake or carb, for $2000. I have a spare Holley 3310, would just need the intake.
I also have a Muncie M20, but the Firebird was a factory automatic.
I could list out pros and cons but they are probably mostly obvious. I am not super cost sensitive but I do like the idea of using what I already have vs buying more junk. Posting to seek general advice. Can give more details as needed. Thanks!