When its hot and cranking slow unhook the MSD box and then crank it to verify if it is an over advanced ign. You have forged pistons and not hypertech pistons so then I agree the top ring gap should be .016 to .017 and the .007 Piston to wall clearence is a bit on the loose side at .007 but it will work. Will most likely be a bit noisey when cold like was said but it will be ok as it's not to tight. If you find the eng is tight and its not the ign then I would think about that .012 top ring gap you have in it. Good luck , Ron