Reg piston was not in a HP block but the combined one was. Slight difference in height between the 2, 68 being taller but neither as tall as the 6 pac. Remember the 69-1/2 6 pac had the regular pistons and LY rods, 70-71 had the high compression 4 valve notch pistons and big rods, externally balanced. I’m thinking the LY rod and lighter pin would get close to the regulars setup with internal balance, with a little metal removal in the piston (30 grams). That’s what I’m looking to do