These are early-production 1972 seats. I'm not sure when the change occurred, but they went to the '73-'74 soft-back arrangement at some point during production. Also changed at different times during production were the Rallye-dash tach (went from 8K to 7K) and the sunvisors (pinned to unpinned).
They could be used in '70-'71 models with the appropriate foams and upholstery. I believe that's true of both E- and A-bodies, but can't swear to it.