I think the last ones (88-89) may have had a mutli layer steel (MLS) head gasket. I think the ajusa is too, as is the HKS. There's a solid copper off summit. The felpro turbo head gasket is good. Multilayer steel is best on the turbo motors. I like the felpro turbo gasket as a good tough carb motot gasket for the price.

A stock head gasket is fine if it's never overheated, and this includes an open exhaust, as cat blockage will fry a 2.6 carb head over time, and a turbo head faster.

The best mod on a 2.6 is head studs and a 3row radiator and good fan clutch and intact shroud.