in order to drop the 4x4 axle 3" from stock 2wd height, i would spend some time checking for axle clearence, particularly between the pig and crossmember. if everything clears, and if your really lucky, you could still get the alignment back into spec without changing anything but the accentric bushings. but more likely youll have to cut and turn the ball joint holes....not a HUGE deal...but you gotta know what your doing.
FYI, differentials arent "AWD", the transfer case is what determins if a vehicle is "AWD" or "4WD".
if you run into clearence issues with dropping the TTB that far, you should look into swapping in an IFS front end from a 98+ 4wd. you could easily achieve your drop with that setup...plus it has the added advantage of being a little better suited for on-road use than the old-fashioned TTB.