[Betterdays]

The headers from the 80 will not fit your 69. LOTS of Pontiacs swapped to Bowtie of choice under the hood simply by swapping the frame mounts from the same body style from Chevy. That said, you keep it all in the direct family and put the Pontiac under the hood and it will be worth more in the end. You wanna go fast cheap, then get a belly button engine (LS) and have fun. I did the small block swap on mine in 1978 and ran it like no tomorrow. If it had a 400, it would have stayed right there. It had a 350 HO. If only I would have known then.....you just don't see many Firebirds with Pontiac drivetrain these days. Be real and be different.🖖

 

[Betterdays]

That stock rear end will hold some power. The 8.5 is too wide for the 69 in the spring perches. Chances are pretty good that you have decent gearing for the 400.