Is it too late to change heads? If the car is not 100% correct anyway, why suffer with those heads? Pontiac adjusted compression ratios with the heads. Others like Buick did it with the pistons. I have a 1970 GTO 400 that I used in my DD station wagon. It had very high compression heads and it sucked. I researched and found a set of 1972 big valve 400 heads with much lower compression. I used those and the engine loved them. I could run lots of timing advance on cheap cat piss gas. After 1973 the heads still had low compression, but the valves got smaller. Testing by guys like Jim Hand reported that unless you are racing, the later heads will flow just fine on the street. You could even play around with 455 heads to get what you want. This site has all the heads and cc volumes listed. Head codes and specs The 1971 and 1972 big valve heads sometimes were missing the end bolt holes for the exhaust manifolds. I guess they saved $.05 on every head. They beveled the flanges of the manifolds so the two inner bolts clamped the manifolds to the heads tightly. This can be done to any manifold to work with the heads. I know any Pontiac V-8 heads are going for big bucks these days. But you can still find deals out there. You could probably sell the HO heads and get several sets of low compression heads.
