I did the swap on the front of my car recently and I love it. I have an 89 as well. Here is a list of the parts I took from a donor GTS.
Struts, springs, ( I don't believe there is any difference in height I just used them because they seemed to be in better condition then mine were.) sway bar and the lower control arms because the SR5 controls arms don't have the little bracket for the sway bar. I ordered new bolts, nuts and bushing from the dealership as well just for peace of mind. From what I have seen and the measurements I have taken the rear seems to be about the same except for the disc brakes back there!! If the donor car has all of the brake components grab those too because it makes a huge difference on mine!!