I don't think the brackets moved. I think the '70-72 seat backs had a provision to be bolted down that the later ones didn't have but I don't believe that effects anything else. The seat bottoms changed in '73 or maybe '74 when they added the retractable rear seat belts. This picture shows a '70 seat bottom and a '74 seat bottom, you can see the '74 has the corners cut back to leave room for the seat belt retractors. But physically they exchange, you'd just have a little bare spot in the corner with an earlier car.
Put some pics up . If not they are modified easy enough. If it's not a bucket seat car originally just add some flat steel plates and put the holes where they need to be . Making sure the seats are parallel to the floor lol