I was just looking over some old photos of parts I've owned and mostly sold, when noticed that the rear seatbelt retractors changed. Most of my pics are from 2 sets of 1978 belts vs 2 sets of 1980 belts. The 78 set uses a centred belt retractor with matching covers, the 80 is offset with the covers matching.
The 1980 version also changes the way it wraps over the mechanism and also has more of a cut-out for anchor bolt and tool use. The 1980 version also has a reinforced belt opening, likely an improvement. I'm not sure if any cast part numbers but the 78 version has PP cast into it for the material used. They would likely not swap easily. I have just been lucky with swapping samples, it seems.
I could add pics perhaps, better wait until morning and even drag a sample or three out. Has anyone else noticed this or knows when the changes occurred? Or perhaps there were several used as being different suppliers of belts. I could look up model numbers for each year but hours quickly go by. These are only the chrome deluxe belts, I have never owned any other type, or looked before typing this.
OK looked at a few used items on ebay. Looks like 79 also has a 3rd version between the 2, centered but with reinforced belt opening on one side only. It would still fit the 78 version fine, but likely not the offset 1980+, unless the offset cover is larger on one end and retains the other end to fit either. Will check tomorrow, I have both, somewhere.