I think any front seat out of any mustang will fit in your 89. I've seen 94-98 gt leather seats in a hatchback before and it looked good! The rear seats is what you would have trouble with. I also had tan cloth in my 89 coupe and I bought 88 GT black cloth seats and they fit perfect and look much better. I also redid the whole interior black.
Heres some pics of a 1990 stang with SN95 seats:
