I may have found the answer to that one. There was a Euro wagon at Pick N Pull, and it had great MB-Tex front seats. {which are now in my wagon
} The passenger seat had a totally different base. The seat would adjust front and back on a slide, but it had no up and down adjustment capability. So the seat was fastened at 4 corners like a normal seat, but there was also a long bolt that attached the outside base of the seat to the side floor frame right next to the seat belt anchor point. Was a long sleeve bolt. So I assume that is also a possibility for the driver's seat.
I just had to replace the passenger seat bottom mechanicals with my old seat.