Powdercoat on 93 Cobra valve covers (powder-coated) and gasket seal issues?

Powder coat is very durable and baked on. I doubt the oil would effect it. As for the gasket. Use some rtv and it will seal the gasket to the valve cover.

as long as there aren't any protrusions to cause gaps in the seal between the cover and the gasket you'll be fine. and i would recommend against using rtv with a gasket. it can cause hard, uneven spots which would lead to a leak. get the felpro permadry gaskets. they're like $30 but well worth it. they are rubber with a metal core which helps them keep their shape, making it easier to install them, plus they have pressure stops on each bolt hole to prevent over tightening. i have 95 cobra valve covers which are the same as the 93 except they say "cobra" on them, and i run the permadry gaskets. haven't had a leak ever. best part is they are re-usable too.