With a stock block(if your set on doing it that way) I would put some aluminum main caps w/studs and do a half fill to the block. Also use some aluminum rods to help keep the weight and punishment down on the mains. You could build a good 499", 512" high compression motor with those heads if they are ported and run easy mid to low 9's at that weight. My 499" has shelf Diamond domed pistons that are made for the RPM heads with EZ-1 cnc'd heads with a small .640 roller that runs 9.40's at 3300lbs footbraking. The combo isn't really optimized either because I don't have much tire under the car to use.