Your rear end is likely narrower than your front end. This was definitely the case on my '97 and '00. The semi float rear end needs 2'' spacers to run perfectly in line with the front end. The full float needs 1.5'' spacers. Not sure what your 89 has, i would assume its the same 14 bolt FF. If your sure you want to widen up the front stance, I'd do 1.5'' in the front and 3'' in the rear. But just getting the wheels squared up helps a lot. I like the look of mine. What is your tire size? 265/75r16's look pretty damn good on my trucks. I believe going any bigger you might start to have rubbing issues. Remember even if tires dont rub on flat pavement, they might when your not on flat pavement.