One more thing............... I went ahead and spent the $ for "Percys" no leak exhaust manifold gaskets. They are aluminum, and a peculiar construction. Actually each gasket is two identically cut pieces of aluminum sheet, combined to construct the thickness of a regular gasket. The mounting holes are relatively large, but that is due to them swedging the holes outward from one side, thus enlargening them. THAT is exactly what I didn't want as I mentioned that being part of the problem fitting regular gaskets.... the sag factor. To solve that I laid them on a nice straight and smoothe piece of wood and used a small headed hammer for bodywork and flattened the swedge out of the gaskets. By doing that the hole was reduced in size. With that done, I cinched both headers up and prayed. I hit the starter and fired it up and still with open headers, I had lost the 'pfffat, pfffat' leak sound I had before. Then hooking up my header glasspacks, it sounded like a healthy motor with no leaks and just the right tone.
For you with problem headers, Percys gaskets are likely the answer..... they were for me......
For you with problem headers, Percys gaskets are likely the answer..... they were for me......