The seat module saga for the Mercedes was more daunting than expected. There were rumors that a module from a W126 or W124 would work, which would have been helpful given those are much easier to find. Not true, as comparing photos of those modules with mine absolutely showed numerous pins in different locations.
There was a module for a 190E on eBay, but it specified it was for a 1991-1993 model. This didn't make sense, until it did: the later cars had the position of the telescoping steering wheel tied into the memory function of the front seat, which again led to pin locations not lining up with my car, which was a very early model with memory controls.
So, I turned to Facebook, and found a 190E owners group that was predominantly made up of users from Europe. A shop in the UK that parts out and restores Mercedes came to the rescue, even going so far as sending video showing the seat moving normally with the module hooked up. Hopefully, this brings this chapter to a close and we can bolt a seat in securely and take the 190E Cosworth for a drive.