head gasket selection

Thickness might depend on where the pistons are relative to the deck. Below deck you can run about anything safely. At or above deck you need to pay attention to thickness so you end up with at least .035" minimum for clearance to the head when the piston is rocked at TDC. If it isn't above 10:1 compression the material isn't going to make much of a difference. Cometic need better surface finish on the deck and head.