340 with Magnum heads

You don't want to get the piston any closer than to the head than .040 as stock rods will streach and since your using a closed chamber head, it might kiss it. Not in a good way! The .028 head gasket you want to use is to small. If its the one I'm thinking of, the mopar performance, it has a 4.060 bore and you have a bore size of 4.070. Comp Cams dosen't give the intake closing point on their cams so you can't figure out the dynamic comp. ratio.