Thought I'd document my experience installing some 4th gen front seats in hopes it may answer some questions and help others down the road.

The seats fit well, but the tracks need to be adapted to work with the mounting bolt locations of the 1st gen. Fortunately, only the back holes need to be adjusted, the fronts line up perfectly.

The rear holes are outboard about an inch on the 4th gen tracks. This view shows the drivers side. I started by making some cardboard templates. The goal was to leave the original track intact as I wanted to be able to continue to use the seats in a 3rd or 4th gen car if necessary. (more on that later)

Once the templates were made, I transferred them to some scrap metal. This was 1/8" steel that I 're-purposed'. It was originally a floor bracket for a Dell server rack, so it was plenty strong.

Once the brackets were cut they were mocked in place to be marked for the bolt holes.

After the bolt holes were located and drilled, the brackets were welded to the seat tracks.

After welding, they were sprayed with some flat black to blend in. Once everything is put back together, they are hardly noticeable. This view shows the passenger side. I used the same brackets as the driver side, just flipped them.
I still have the templates I used if anyone would like them, just send me a PM. I'll also work on posting them here.
I didn't end up using the seats in my car. Instead they'll probably go into my son's 3rd gen project (which is why I'm glad I didn't cut out the original mounting holes on the tracks). As you can see, they originally had gray velour covers. I bought what was supposed to be some black vinyl ones, but they were actually gray as well. They didn't match the original seats very well either.