I fogot the 85 has 10in rear brakes and the 92 has 9 in dont know if that will a upgrade or not
Swap the passenger axle shaft from the 92 d30 (front) after getting the correct seals from somewhere online and your front will be good, but that may be as much work as simply swapping the gears/carrier.
The 85 shouldn't have 3.73 unless you have the "gas" package or whatever, which is SUPER rare. It's most likely 4.10's from that combination.
Your 92 has a d35, not d30... but anyways, some info: the 92 d35 should be c-clip, while the 85 is the "traditional" style. If what you say about the brakes is true (the older are larger), then the older axle is an upgrade in every way (stronger, easier to repair, more braking power, and deeper gears)!
Everything should swap directly in, but there are three options for the front end (axle shaft) problem:
1. Steal the 92 shaft and get new seals and vac-disco cover plate.
2. Swap gear/carrier from 85 to 92.
3. Posi lock the 85, either with the "perma-lock" or selectable one.
If you're lucky, the 85 has part-time 4wd, then the whole issue is nulled...