383 Flat top pistons.

I'd be looking at a different set of pistons. I don't know what that company offers right off the top of my head, but I do know KB offers some really nice hyper-U slugs at a reasonable price that'll bump up the comprsion nicely and still letcha use pump gas with generous valve reliefs for big lift cams. Max lift on a cam won't be an issue for 450 HP and KB slugs.

OH, standard or .030, same price thropugh summit racing here --> http://www.summitracing.com/parts/UEM-KB162-STD/