1970 hp block it is from my 6bbl car, numbers block. Both front cylinders are .016 in the hole, both rears are .017 in the hole. Never milled. An .024ish head gasket would mean no milling. 1009 will not work on this block, has chamfer, the non hp 69 was fine with 1009 same.030 over bore and pistons. So it is real hit and miss.