https://www.bopengineering.com/beltd..._topend3.shtml
"Pontiac Steel Core Valve Cover Gasket
The BOP Pontiac steel core Neoprene (rubber) valve cover gaskets are the ultimate in sealing and reusability. The steel core maintains the shape of the gasket for improved sealing especially in vacuum pump applications. Gaskets will not get sucked into the valve train area and or tear like cork. At 3/16 inches thickness (.187") they also aid in clearance issues with roller valve trains.
Pontiac Steel Core Valve Cover Gasket (pair) (VCG45R)... $19.99"
BOP Engineering also has a one piece oil pan gasket