You’re blowing head gaskets on a naturally aspirated slant 6 and you think the solution is boost and copper head gaskets? You should probably dial in your tuning skill on the NA engine before diving in to the world of boost. Sorry if it sounds like I’m being an ***, but little problems become BIG problems when boost is involved. As for a gasket recommendation, copper with o rings and receiver grooves become necessary around 30psi. You don’t need more than a good cometic MLS gasket and head studs for around 8psi.