Spoke with Legendary today in fact - going to just go with the notched heel pad based on replies here and from some 71 B Body experts. My guess is it had the wrong carpet installed or they only had this carpet available.

This car appears to be built in late June ‘71 at St. Louis, trim panels have dates of June 8, looking for other date coded items to narrow it down.

Another anomaly is it has all black seat belts, all matching date codes that have never been removed based on the condition of the anchor bolts. even though the car has blue interior.