Duster fold down rear seat
Ok, so I grabbed a couple pictures off the 'net and I don't know that your '72 seat bottom will work. At least not with the retractors installed. The notch in the seat is bigger than I remember it being, so the frame is likely different on the earlier versions that didn't have the retractable seat belts.
Giant seat belt retractor
Notch in the seat
Frame from below
Earlier seat bottom, doesn't look like there's any notch at all