above deck ?

Depends on the combination - but I routinely build with them positive deck. If you want to use the cheaper head gaskets at .039 thick and run milder street type compression ratios you have to in order to get an effective quench. The only engines I build with more than .035" quench are 400-based strokers because of the short piston and big bore. There's more rock at TDC, so you need a little more room for it to wiggle.

596 heads - open chamber. There is no quench, and you have plenty of room in there. The issue might be static ratiom with flat tops.
What cam are you running?