Thanks for being a part of our nations military several of us on here are veterans

A reason that pistons crack like that after a rebuild is that new rings in a used bore( especialy with a tight spot above the ridge worn by the old rings will hit the top ring and crack the land down toward the second ring

If the crack appears to have been upwards--second ring probably hooked on top of block from a poor fitting ring compressor and/or a heavy hammer in inexperienced hands during install-also since block is overbored,there may (probably) not be a slight bevel at the top of the deck surface--------

Your going to need new pistons, rings and install on your rods ( not pressed but the electric rod end heater)