Head gasket recommendations for magnum

Off the top of my head I don't know exactly where to look, but any variation would be in machine tolerance rather than casting for the fire deck, the only problem is finding a consistent place with two opposing machine two surfaces to take that measurement from. without a head in front of me to look at, I can't think of any machined surface that is 180 degrees parallel from the face. I'll get back with you on that unless somebody beats me to it.