1971 production ended first week of July 1971
1972 production started mid-July 1972

door sticker (if original) would show "month finished" & a comparison of the sequence number on a St. Louis broadcast sheet would indicate which came first

the latest St. Louis HEMI car I have info on was "SCHEDULED" 602, there is a later scheduled blue HEMI GTX, scope I can't find info on it right now