The first year for the larger pilot tip was actually 92, not 91. Just put a 91 4.0 in front of a 98 AX-15, and we needed the CJ bushing.
Your driveshafts will be fine, the Pukey and AX-15 are the same length. You will need a 23 spline T-case for your AX-15, the one on your pukey will not bolt up.
You'll need the AX-15's slave. I recommend looking for a 94+ AX-15 bellhousing/bearing retainer/clutch fork to get an external setup.
AX-15 crossmember would be a good idea, since you'll need a new mount anyway. You shouldn't have to move the crossmember back, the Pukey should be on the middle and back holes.