Your best bet is to search junk yards or a parts XJ for all the addition parts needed.
Look for a 94+ XJ with 4wd. It will have the external slave bellhousing. You should get the Tcase also. The tcase with you BA10 will not mate up to the AX15.
Also get the cross member, transmission mounting bracket, Tcase shifter linkage.
The AX15 from a 98+ XJ will have a lager input shaft tip, so you will need to change the pilot bearing/bushing.
If the AX15 comes with (or you convert to) an external slave cylinder, you should swap the clutch disk/pressure plate. (The pressure plate is the same for a BA10 and an AX15 with internal slave cylinders. The PP changed when the AX15 switched to external.)