And when you go to NAPA for those valve cover gaskets, pick up an aerosol can of Permatex RTV dissolver so when you want to get everything removed from the valve cover it'll be a much easier job.
I have used both the cork-style gaskets and the composite ones (usually black, but I've seen green ones, too) over the years with bolt-on valve covers (the worst, I know, but what'cha-gonna-do when you're a cheapskate?) and have about the same luck with either. I will lean toward the cork ones if I have them, but usually just grab whatever is in the gasket bin. Usually I'll buy a 10-pack of VC gaskets at VW show flea markets whenever I'm running low, but NAPA is handy, too.
Like Kelly, I just use a liberal film of automotive grease on the gasket. Makes getting the cover off later much easier. If you feel they're gonna distort and leak, Permatex them to the cover. But I would suspect the flatness of your current cover mating surface.
I remember running out of VC gaskets at an autocross once, so we just ran a BIG bead of Permatex around the valve cover. It sealed perfectly and lasted way past the end of the season, but I almost had to use Dynamite to get the damn valve cover off.