NDTIII, you are mostly correct, the ASTM's and ASME SA's contain a statement at the top of most standards that proclaim one to be identical with the other, in fact, in most cases, ASME purchases a license from ASTM to use their standards with an ASME heading. There are, on occasion, however some "tweaks" or additional requirements ASME imposes, not often but they do happen. Also, in many cases, for your fabricated item to be code stamped with an ASME Stamp, the material must be SA type material. I don't believe ASME VIII mandates SA materials however, please correct me if wrong.