Head gasket thickness

383/496. Trick flow 270 heads. Not sure if open or closed chamber. How could I tell? I will look now. 13 :1 compression. Dome I believe is 6.5cc. Machinist says he can cnc the pistons to .005 out of hole. That is his preference . But he wants to put gasket and head on and check valve to piston clearance first. Feeling a little confused