what is the best style casket to use with the big block mopar aluminum valve covers? cork or rubber? heads are stock cast iron. are these good covers?

what about their sealing ability?

Don't ask...Some are better than others...At least I haven't heard of Big Blocks hitting the intake manifold like small blocks do...I've seen guys post about having The gskt surface milled but that seems like a spendy fix for a cover that still leaks at the breather grommets..