89's being the first year were weird for the auto's. They could have been 3.08's or 3.27's being the option. All 5spd SC got 2.73's. All SC have an 8.8 center section.
You can do 2 things to check and see what was your stock gear ratio. Look on the door post for the build sticker, under AX, there should be a letter or number code, get this and either find a decoder or post on here and someone will tell you what it is, or you can check out your center section of the rear end. There should be a metal tag with the ratio stamped on it. For a trac-loc 3.27 it would read like this 3L27
