Advanced adapters. The 88 bushing will not fit the input of your ax-15. When I put my 4.0L HO infront of my early style AX-15 I used a 258 bushing and tunred the OD down in a lathe so it would fit the 4.0L crank.
It's also a function of what you are plugging into it. Different transmissions over the years have different pilot bushing ID needs.
That is what I was getting at. Mine was a 1990 ax-15 which had the small input they used behind the 258. If your ax-15 is the stock 1994 that came with it the input will be larger. Now if you did have the early style ax-15 you would just use 80-91 6 cyl. CJ/YJ bearing. Your best bet would be call Advanced Adapters and tell them what you are trying to do and they will hook you up with the right bushing.
I don't remember which year the pilot snout increased from 0.590" to 0.750", but if you have the smaller one, a stock pilot bushing will work from an '88. If you have the larger one you'll likely need to get a custom one that fits the ID of the crank shaft and the OD of the transmission.
White '94 YJ Sport Black '98 ZJ Laredo - 45x60 Surco Rack - 2" Budget Boost, Addco Front Swaybar