Do you by the exhaust manifold gasket to match the header/manifold, or strictly to match the port design? I've got a 70 - 72 BB and can't seem to find a gasket that matches. It is not exactally square, definately not round, sort-of ovalish. I have the square port gaskets but they don't look like a good match and don't want to pull them out of the packaging to test it out (summit SUM-111410 copper) . I'm running headers, not manifolds.

They typically don't match up too well. I'm also running the summit copper gaskets on my BBC with Hedman headers. Those copper gaskets work really good. I've taken off my headers twice and have used the same copper caskets and they still seal. I'm sold on the copper gaskets.

THe Hedman headers have a weld bead on the flange that is gound flat but not flush, important that the gasket match the bead, a square port gasket on a round port header will not seal. I am using a thick aluminum gasket I got from Jegs, works very good but needs 1" header bolts rather than 3/4!