Just a re-fresher. Diamond Pistons(overstock) #30021, originally for the Ford Mod.4.6L with large liners. 3.700" bore with 1.220" comp. distance.List $76.70 - 50%. ACL(marketed) top hat liners, actually made in Spain, appear to safely "clean-up" with 3.766" bore. This makes the sbc(305") .030" oversize piston, a possible option. These "should" be better suited for the Merlin heads, as they are closer to valve inclination of the "305" piston. NOT an endorsement, my attorney said to say this, use at your own risk. Cheers, roverman.