AX15 will cost you about $200-$300 on CL. About $75 for the bellhouse to adapt it, and then about $120 for the clutch kit. You will need your front and rear drive shaft lengths changed, but you need that anyway with 6" of lift if you want it to flex without any problems.
The thing is that the tires arent what kill the AX5 exactly.... The harder you make it to move the Jeep is what makes a difference. 6" of extra height at 65mph makes a big difference. Add big tires and small trans and the trans will give out since nothing else is going to. When you put an AX5 next to an AX15 you will see what I mean. It is like Hercules VS PeeWee Herman.
Take care of your trans and Suspension, then get tires when you have the cash.
Complete rebuild axle/engine/everything swap in progress:
Parts already gathered for assembly: 2001 Ford 302, 1990 Mustang GT 5.0 ECU and wiring, NP435, NP205, Pair of axles from 04' F350 SuperDuty (Sterling 10.5 Posi rear, Dana 60HP Front-Both Disk Brakes 3.73 Gears), 37" H1 Tires, 9" lift TJ Coils for 2 link conversion in front, Stage 2 Clutch Kit, 3 Row Aluminum Radiator, Chevy Astro Steering box (4" front Stretch), XJ Rear Leaf Springs (6" Rear Stretch), and lots more.