It really depends on the seat style in particular. I believe that, just like the frames and runners, they were well used throughout a lot of model years.
I had to replace the Lower seat frame on my 92 and it had the basic high back seats. I found the replacement out of a late 90's, early 2000's Explorer. It was a simple switch to replace the old back onto the new seat and the old seat covers worked on the new frame.