Having done this swap I will share what my father and I learned:
1) The front axle is almost a bolt in swap. The pivot bracket for the passenger side arm has the be changed for a 4x4 bracket, knock out 4 rivets and your good to go. As far as the front axle itself, look for a 91-94 Explorer front as it is the better/stronger dana 35 axle. Depending on your uses you may also want to grab the rear from the same explorer to get the 8.8 axle. Some Rangers came with the dana 35, but explorers are a definite and they have the 31 spline rear, where most Rangers are not.
I would suggest getting the 4x4 steering also. Our axle came less steering and we used the 2wd steering but had to cut and weld it to work as it was too wide.
2) You will need a manual transfer case. You are looking for one from a 90-97 model ranger with the fixed front output. Also grab the front driveshaft from the same truck or the explorer the front axle comes from. You will also need the shifter and bracket, doesn't matter what transmission was in it, after 89 they were all the same. Case in point, my 94 explorer is a 5 speed with a manual case swap and an "auto" shifter bracket. Older model Rangers had a manual and an auto bracket that was different.
3) With the transmission you are in great luck as second gen bronco 2 2wd vehicles were produced with 4x4 transmissions in them and a dummy transfer case. Even your rear driveshaft is a 4x4 shafts. Installing the shifter is easy. Remove the front seats and shifter/boot (if 5speed) and peel back the carpet. Remove the floor plate, and cut a hole in it for shifter movement.
Theoretically you could use an electric shifted case, and devise some sort of PTO-ish cable shifter, but the manual case is easiest. If you aren't looking into heavy wheeling, the factory 7.5 rear axle on the bronco is fine. If you will only ever have stock size tires and never go off-roading more than through a pasture or old dirt road to deer hunt, you could get by with a dana 28 front, but anything over 235/75/15 tires, and any type of throttle off-road has been know to grenade the little front. My front 35 has withstood three different sets of 33's, two of them through Uwharrie, the last a set of km2's that saw woods use, mud use, and even got used to pull ton trucks into the shop on pavement. While the last part is pretty stupid, it just goes to show what they can take.
