1969 Firebird engine choice

As much as I'm a huge fan of Pontiacs, the engine tech is really long in the tooth and it's hard to justify the hippo-sized weight with the options out there.

My 67 LeMans convertible is getting an LS6-headed LQ9 and a T56. Easy 500+ hp with the right wallet.

If I were keeping it "in the family" and old school, hands down, Caddy 500. Only about 30 lbs heavier than an SBC, way lighter than a Pontiac, and 500 cubes means super easy to get whopper power without having to open the big wallet for all the other stuff like gears, converter, etc. I had one making north of 400 hp in a 66 Bonneville and I actually opted for a lower-than-stock stall with a Diesel converter in the TH400. Traction was still a problem with 3.08s.

Grab a later 500 (lower compression), pocket port the intake, fully port the exhaust, Edelbrock intake, Qjet. BBC headers fit if you cut the flanges off and weld on caddy flanges. Mild cam in the 204/214 duration area. 450 hp and well over 500 ft-lb, and can take a stock converter and highway gears and 87 octane.

From the options you listed I'd get the 80 Firebird and use what parts you can. Since you can use seats as well as engine/trans then sell the rest, that appears to be the most economical choice of the options you listed, and keeps it all Poncho.

That said, I'd sell the parts you have and go with a modern LS also. Main reason is the EFI. Or do something really "weird" and use a Vortec 4200 or 3500 straight six or five. That would be a unique ride with the power of a carbed SBC and the look and feel of the Poncho OHC 250 six. With 270-275 hp (NET -- equivalent to ~352 hp in the 60s GROSS rating system) the 4200 would be great and surprise a few people in the relatively light 69. Even the 220 hp (281 hp GROSS) 3500 wouldn't be a slouch! For a just jump in and go car you can't beat a modern computer controlled EFI engine. It's a bit more expensive than a carbed engine, and if you want to play with tuning and different parts it's difficult to deal with, but then again there is enough reliable power in stock form that you don't have to. Modern tech beats old school brute force every time! Stock V-6 Toyota Camrys beat 60s muscle car quarter mile times with a four cylinder that's just under a third the size of a Poncho 400 (2022 Camry 2.5L four (152 inches), 15.7 quarter miles (14.1 with the 211 inch/3.5L V6). Even a modern V-6 would equal great performance in the 69 Firebird body, but I doubt you'd want to put a Japanese engine in one... that might just be too much for American muscle car fans, and would hurt resale, whereas any modern US engine probably wouldn't.

I might revisit the LS idea. I keep thinking about it. However, I already bought the '80 Firebird, so my default now is to use the Pontiac 400.

Now the looks part. My 1969 Firdbird has a plain hood with no hood scoops. I am thinking about switching to either the 400 type hood with smaller scoops, or the Trans Am style with bigger scoops. I think Trans Am style looks better. However, I am not planning to try to clone a Trans Am overall, so I am not sure if it will look out of place to people who know the model if I use the Trans Am hood, a Camaro rear spoiler and a single paint color (probably either silver or midnight green - car was originally limelight green). Maybe nobody cares about that since the Trans Am hood is an upgrade whether or not the car is a Trans Am. Since the car will have a Pontiac 400, I could alternately use the 400 style hood and do sort of a Ram Air clone to be a little closer to correct. But again, not sure that really matters at this point since I am not doing a faithful restoration.

Also trying to figure out what wheels to use on it. I have a spare set of 1970 Z28 wheels with peeling chrome. I am thinking about getting them powder coated. I've also thought about getting C5 Corvette wheels.