If you use the proper thickness head, gasket the piston to head remains correct. As does the piston to valve. If it’s .020” out of the block, run a .060” gasket. No machining necessary. A .060” gasket will be pricey. You’ll need Cometics or something similar. If you chose to run a open chamber head the entire chamber has to be equal or greater to the bore size. And in this case piston to valve would be closer. In most cases quench depth would still be to great to be of any help.
Doug