Small block valve cover clearance??

I use Fel Pro 1646 gaskets, they are laminated 5/16" thick and have a steel core. My valve covers are similar to the OP's and I used SS socked head cap screws from Fastenal. A little bit of silver anti seize takes care of the corrosion when used in an aluminum head and for a valve cover I don't tighten the bolts on mine enough to worry about yield strength.

Fel-Pro 1646 Fel-Pro Performance CorkLam Valve Cover Gaskets | Summit Racing