340 with Magnum heads

I thought stock 340 pistons were above the deck. I would be concerned about interference with the closed chamber magnum head. If you go with an aftermraket flat top piston at zero deck and a typical 0.040" thick head gasket you will have about 10.6:1 compression. This is the set up I have in my 360 and I too am using the XE268H cam. My 360 is a strong runner.