Good post, Gary.
Permit me to add one more note. In the 60's, only a few M1 rifles were available, mainly those military aid rifles brought back from England, and some from DCM sales. The Army scrapped a bunch of receivers by cutting them in half with diamond saws and selling the pieces. Several enterprising companies bought the pieces and welded them together. No attempt was made to match pieces, so an SA rear could be welded to a Winchester front. (See http://www.fulton-armory.com
for more info.)
Many regular rifles were made up this way, but the so-called "rewelds" were a favorite with builders of "tanker Garands". The real hooker is that the M1 was still in war reserve and those receivers were scrapped for a reason - they were worn out or defective in some way. This, to me, provides another good reason to avoid "tanker Garands".