the 4.875 diffs are NOT the same as thr 4.90 diffs.

The 4.90 diffs are way much bigger 12bolt v 10 bolt. They are not interchangeable.

If your vehicle has the 3.5l motor then it should have the larger diffs. In Aust the standard ratio was 4.636 , the 4.90 diffs you speak of were fitted to diesel vehicles in Aust.

When I had my 97 NK 3.5lDOHC I swapped in 4.90 gears but found it generally a waste of $$$$.

However if you guys are going from 4.30 diffs to 4.90 then IMO that is a more marked improvement.

cheers

97 Exceed, 3.5l SOHC auto, 4.90 gears, ARB front locker,rear Harrop E-Locker, Magnum winch, dual transfer cases also 2008 NS swb Pajero, front bar & winch