Ponder this: Our original (from new) B382000078LRXFE came with the narrow caps. In the barn is B382000004LRXFE with the fat caps. I have found several drive side narrow caps that are cracked or broken where the fastener screw hole is so close to the edge.
Randy, the narrow B post do have a habbit of cracking where the screw goes through as the casting isnt as strong as the early style.
As stated the SV and MKIA had the narrow ones as a design change. I would assume this was to stop slight door misalignment causing the B post to chip the door paint.
Its possible your very early mkia Might have had the early style caps fitted ..but i would think more likely they were replaced at some point as you often see late style on early cars (even s3 alpines) and even mixed sets.
As a side note rootes also had 2 types of B post on the early SI/II alpines... Either they were really bad at getting B post design right... Or were chasing the perfect B post cap š