Why not have a machinist face off the gasket surface of the filter housing flat again? It's a fairly simple setup in a lathe with a 4-jaw chuck, and you'll eliminate the source of the gasket distortion. Rubberized cork would be the material of choice, but you're whizzing in the wind trying to seal against a warped surface.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!