I used to use stock bolts, but without the rubber washers under them. Not the cleanest but it is hard to get the grommets down between the fins. I am thinking of changing over to studs with rubber on the inside of the valve covers and a crom nut on top. ( I'm currently running Edelbrock covers) It would need to have enough 'squish' to allow the valve covers to seal at the perimeter though.
