Does anyone know the differences in headgaskets? It'd be for a ford 351w, raw water cooled.
Most non marine composite gaskets have a steel core that can rust. They are made to operate in a system with a rust inhibitor like anti freeze or some other type of inhibitor.
Marine composite gaskets have a stainless steel or copper core.
Most multi layer steel gaskets are layered stainless steel and are fine for marine use.
Carefull though, Felpro for whatever reason feels compelled to refer to some of their composite gaskets as "MLS" all though they are not technically layed.