Welcome to the real world - you folks in the US have it easy when it comes to returning incorrectly ordered (or supplied) parts, for the rest of us, it can amount to you bought it, it's yours, and that's one of the reasons I don't have an air locker in the back of my GV, I can't risk dropping a grand without being certain it'll fit.
The only way you're going to get the question answered is to pull the rear third, count the number of bolts and measure the diameter of the differential case. The Suzuki parts catalog shows the same part numbers for the rear differential case from 99~05, if you have a manual transmission, but, automatics had a change between the 00 and 01 years.
I'm fairly certain you have a 12 bolt diff, but, whether it's a 108 or a 118mm ID is where the real question is, and then you have a Tracker, all of my info is Suzuki and not everything gets carried over.