If you can find anywhere on the intake to head mating surface that doesn't have a gasket protruding from the crack, you could get a measurement there and see roughly what the compressed thickness is. if it were me, I'd just get a set of Fel-pro run of the mill intake gaskets and call it good. As said before, thickness doesn't really matter too much. The two surfaces should be parallel with one another.
As for valve cover gaskets, I assume that's what you referred to in the title, I use nothing but rubber gaskets with the steel shim core now. Best, by a long shot, of any other gaskets I've ever used, and re-used. Usually available at any supply house.