Plan A: adjust alignment of headers by lowering flange holes 1/16". Install oval copper gaskets if I can find one that fits 88650 hedman headers. Try to verify headers mate correctly before installing new gasket.
Plan B: Make 1/4" aluminum gasket and put soft gaskets on both sides.
Plan C: Fabricate better fitting flanges from 3/8" steel and mig weld then fillet weld with bronze. Not my favorite plan since I applied ceramic coating which I will have to completely remove (not easy) then reapply.