I've had the best luck and the most anecdotal good references on Kopper-Koat and Indian Head copper based gasket sealants. I've also heard that Hylomar (DuPont, I think) is very good, but have not personally used it. I talked to a good engine builder the other day about Frank's engine leaks, and he said that he had bad experiences with MLS gaskets, and had gone back to recommending solid copper head gaskets and steel block Oringing (cylinder bores only) on forced induction engines. I think Summit still sells copper head gaskets. And Hylomar...