Yes, the rear is the same in all sidekick and tracker models. They are 26 spline. The only ones that are different are the fronts.
The only thing that really changes in the rear is the differential ratios, if you have a manual, you most likely have 5.12 gears, if you have a 3 speed auto, you have 4.62's, and if you have a 4 speed auto (overdrive) you have the 5.12's.
Also, there are 10 bolt and 12 bolt rear ends. Usually 92+ are 12 bolt (most of them with ABS brakes in the rear) and 91- 89 are usually 10 bolt.

I understand you are going to make one, I'll tell you that purchasing one will only cost you $99 bucks, otherwise, why not just weld the rear? (lincoln locker)