It depends.
VS Ute will have a live axle WB78 diff, 0575 gear set with 0578 4 spider centre.
There are a few different possibilities for the VT. Series 1 VT SS will have IRS but the diff will still run 0575 gears and 0578 4 pinion centre which will fit in the earlier VN-VS diffs however the series 2 VT SS will have the LS engine which will have the BW80 series diff where nothing is interchangeable with the earlier models internally however the M80 will bolt into a VP-VS IRS car as a complete unit.
As mentioned earlier, chances are the factory LSD will most likely be worn out but these are definitely rebuildable and done right can go reasonably well. There are various options out there for replacements.