i like to run zero deck with .041" gasket. I ran a 598 on the dyno once that was down to .035" total turning to 7500 and when we pulled it apart the piston part number was stamped onto the head. (it was a test engine and the pistons had a part number eched on the top) That was a 630ish gm piston on a scat H beam rod with .007-.008" clearance.
Just another vote for .040"+
Steve