The 85-89 pistons are .025 taller than the regular stock 318 pistons, so if the std. piston is .060 below deck and the square decking takes .020-.025 for a cleanup of the deck then the .025 taller 85-89 pistons and you are now .010-.015 below deck with a 85-89 piston. Now add a .020-.022 MP gasket and you have the right quench with 302 heads. Now use the right camshaft and the HP and TQ go's up and up. Cylinder pressures mimic 12.5:1. I thought that you had done this already. LOL