
I believe my '66 has the OG covers on them; basketweave centers that rollover the top to about 3" down on the seat back. The rest of the seat back, as well as the "margins" of the seat faces, are smooth. This matches what I've seen in other 1966 Beetles and pictures online, so I've always considered this the OG style for 1966.
After getting on the phone with JBUGS and TMI this morning, I discovered that TMI has recently come out with a new "rollover" style (43-1135) for 65-66. These look fairly accurate for 1965 but still don't match well for 1966. This design stops the basketweave pattern on the front face of the seat back, with the smooth "rolling over" from the rear, and no piping across the top at all. Although this shape is slightly more correct than the previous 65-67 style from TMI, it appears to be 1965-only. Here is a photo of the 43-1135 from TMI's customer service rep:

My next step was to reach out to Mario (VW Division Sales Mgr) at TMI. I described my seat pattern and he replied back with a photo of their 43-1014, which looks identical to my original seats. This is supposedly their '67 style. According to their website they only offer this style for the front seats. Mario claims that the matching rear seat is 43-1115. Note that JBUGS doesn't list either of these codes on their website, but I'm sure they could order them if I call them directly. Here are pics from Mario of the 43-1014:


These are the closest to any I've seen of a true 1966-correct seat cover. They have the correct pattern on both the front and back, with no piping across the top of the seat back.
Anyways, I don't really have a question per se, but I thought perhaps this information might be useful to other '66 owners. I'd like to hear back with your own experiences with any of these seats and if you're aware of which style is canonical for 1966, and perhaps if there were any mid-year changes (my '66 was built in January 1966). As I managed to scratch up one of my new seats anyways, I might end up ordering the 43-1014's and re-reupholstering again.