The way yours are upholstered now, they look like #4 to me...no horseshoe bottom or backrest. The difference being that yours has tucks in the backrest and #4 doesn't.
My July of 71 production 72 MY Bavaria 3.0 came to me with the original upholstery so it was easy to duplicate. #3...horseshoe bottoms, no horseshoe backrest. Their #3 shows tucks in the backrest, but mine arrived without tucks just like my originals. I assume the tucks can be put in at the time of installation if desired. I had mine installed without the tucks to match the originals.
I believe we do need Christoph to help determine the style yours came with originally. I think I have his email addy. PM me if you need it.
I'm not sure what part of the seat back you wanted a picture of. Here's mine. Let me know if you need something different.
World has the embossing equipment to duplicate the unique embossing. I would think it would be the same for the 73 MY. The seats will then match the door panels if you are able to reuse them. If not, World will sell the embossed material by the meter.