Your tranny should be the MUA-5, with an integrated transfer case. 4.56 R&P sounds right. Since yours is a '90, the t-case should have a slip-yolk rear output. Those gears are for a fixed-yolk rear output. You can make them work in your t-case; but will need to source parts from a fixed-yolk case as well. There is an old post that outlines what all needs changed over.

[edit] Meh... I'm feeling generous today. HERE is the old thread I was refering to instead of making you search for it. Don't expect this to happen all the time. <img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/lol.gif" alt="" />