I don't have this down to specific part numbers, but I like the Felpro cork composition. I attach them to the valve cover with RTV Black and let them dry. while they are drying I make sure to put bolts through the valve covers for alignment. Then I coat the other side with rtv and allow it to dry.
Wipe them down and put them in place. As long as you do not destroy the gasket by over tightening, they will seal for years.
Just my $0.02 worth
