Update: both seats are now installed. The passenger seat has a different bolt pattern for the manual seat track than the driver side had with the power track. I tried to take plenty of pics to illustrate everything....
Here is the piece that doubled as the riser and as the locating jig for the mounting holes. As you can see, it worked well.
And the back side of the original seat. Notice the broken bolt on the left side. The right side also broke when I tried to remove that rail.
Here you can see the newer track's hole locations are spaced differently. They're also too narrow to try to reuse them.
Here, the new seat's tracks have been removed and revealed multiple hole locations on the back side of the seat. The driver seat was completely different and I had to relocate all of the mounting holes. But as you can see, a pair of them lined up well with the II's seat tracks, I just had to drill them out in order to use the spacer pieces so the tracks would clear the framework.
After getting them mounted, I used my jig to double check the track's mounting stud locations and bolted it into the car.
Now, it's time for a serious bath and a test drive to confirm my wiring project is up to snuff.