Bill,
I have a 1971 Chevrolet Suburban guide that describes the seats as follows:
- A52: standard seat or optional custom bench seat (no center or rear seat)
- A50: optional bucket seats
- AS3: optional center seat only
- A80: optional center and rear seat (a rubber floor mat for the rear compartment was included with this option)
When ordering AS3 the center seat is wider than when ordering A80; 58.25 inches versus 50 inches, respectively.
I hope this offers some help.
Phil