For your application, 4X have press in studs, not too reliable for a mild build up. As far as milling heads, you will have to have the intake sides milled after .025 on the deck side. I would recommend 6X-4 or 5C heads..
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
