I am building a 414 SB stroker (.020" 0ver 340 block). I am going with KB745 pistons with 20.5 dish, Felpro 1008 .039" head gasket with 4.18" gasket bore, and closed chamber eddie heads milled to 62 cc. This will give me 10.3:1 compression. I could go with Cometic .036" with 4.060" gasket bore to get 10.47:1 compression. But 10.3:1 will be plenty to make good power on pump gas premium. You can play with some numbers with this calculator:

http://kb-silvolite.com/calc.php?action=comp