I have seats from a late 80's TA in my car. There are a couple of ways of installing IIRC. The first involves replacing the seat tracks of the 3rd gen seat with those from your second gen. Supposed to be a direct swap, but I didn't do this. I made some brackets that extended the front of the 3rd gen seat track to fit the existing holes in the floor pan. Pretty easy to do and the seats fit without problem.
I had the original back seats recovered in the same material as the TA seats so no issues with fitting a 3rd gen rear seat into a second gen.
I will note that the seat bottom (the part your butt sits on) is very short. I believe Gary discussed this several months ago. I can barely get 1/2 of my thighs onto the seat when sitting upright. This isn't too much of an issue on short drives, but for anything of any length, your butt gets pretty sore. JMO. Good luck.