I know when my engine was originally built it was.010 above deck. of course when I read the paperwork that's how much they shaved off the top of the block to get it square.. so as it was discussed with me the engine builder instead of using a fatter gasket then the 1008 at 39 he gasket matched countersunk the heads around the edges so many thousands to accommodate... He seemed to be comfortable at a minimum of .030?