Using Hughes retainers and my pistons.050 down in the hole I only hadPiston are usually ".050 -060 " ,in the hole. Valve train is limited to ".510 - .520 depending on valve train decision. To be honest, I don't see a need beyond "480-490 lift " unless the heads flow more than 260 ...270 ,on the intake side....
.020 clearance retainer bottom to guide
Clearance with .512 lift. Iunderstand that Hughes now has a retainer that will allow more valve lift. Not sure of the head gasket thickness