I don’t mean to offend anybody, and maybe I missed something reading this but I wonder if you guys aren’t way over thinking this and missed the obvious.
“….I know the old gaskets didn't come off all the way because the were corroded and baked on to the point that even using a heavy file on the faces to get the most of the old gaskets off then a mill file to smooth it out….”
ALL the old gasket material MUST be removed from both the manifold and the head for the manifold to seal. From the looks of the picture of the manifold I would almost bet there is (was) material still left on the head. Cleaning the manifold can be a PIA and the head even worse, but if there is any old gasket left on either you can do this 100 times and it will still leak. You can pretty well tell where it was leaking by the carbon trails on the gaskets, and that’s where you need to spend some more time cleaning.
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