Stock headgaskets seal very well, and a lot of drag racers use nothing but stock gaskets. Golden Eagle also recommends you use stock gaskets with their sleeves. They also happen to sell precision overbored stock gaskets that they machine in-house. If you still don't want to use a stock gasket, or want a different thickness, go with a Cometic HP, or the MLS if you're having o-rings put in. Copper spray is this stuff that comes in a can. You spray it onto both sides of the headgasket and it becomes tacky when it dries, and stays tacky. It helps the headgasket seal.