I have a 2000 GV and ive fitted lockrights to both diffs. You use the 1510 sierra lockrights. they fit in nicely. The front is easy but will require manual hubs.
The rear is a little harder. You really need to machine/grind a small lip off the side gears where is sits against the center cross pin block and shim up the difference. This is so the side gear sits in better and will reduce the ammount of play . It will fit and work without the grinding but it will annoy you to no end. Alternatively you could run 26 spline sierra/sami side gears.
B4T