You need an NP231J transfer case with a slip yoke eliminator. Or you can buy a transfer case without one, and then buy the SYE kit and add it yourself. It’s not hard to install.
When people say “input shaft,” they are incorrect. They mean the input gear, and those have different stickout lengths as they go into the seal on the back of the transmission. So stick out length is based on transmission. An automatic places the seal further forward, so you need the long input gear to reach to the seal. A manual almost always needs a short input gear. And by “need”, I mean that is all that is required. A long input gear can be installed onto the AX15 transmission, it’s just longer than necessary and the seal will still ride close to the transfer case as if the gear were a short one.
for some unknown reason, Jeep shipped 98-99 TJs with AX15s using long input gears. Not because they needed to, but they just did. No clue why. YJs and 97 TJs all shipped with short input gears on AX15s.
Next up is input gear spline count. AX15 needs a 23 spline input gear. So in your case you need a 23 spline short gear, but you could do a 23 spline long if you needed to.
Worst case, take the gear out of your current transfer case and install it into the new one if you can’t find a case being sold with the proper gear. Only downside with that is its more work to disassemble the transfer case that far, and you’re basically doing a whole rebuild at that point. No big deal though.
also keep in mind, an old style input gear (1994 and prior) will not work in a 95+ transfer case, and vice versa. So try and find a guaranteed YJ case if you can. Otherwise if you get a TJ case, that’s fine, but if the input gear were wrong, you’d need to buy a 95+ input gear (short, 23 spline, long in a pinch) that would work in the 95+ YJ or TJ transfer cass. It has to do with gear cut, the input gear’s teeth were cut differently in 1995 and the transfer case and planetary assembly teeth were modified to match that.
The year designations of 1994 vs 1995 are not dead set either. Some 94s got the newer style. My 94 was built in oct 1993 and it had the old style. Some ways you can tell are caged needle bearings on the output shaft, and also you can tell by the bearing style on the input gear. A narrow bearing is later, wide bearing is older style. You can figure out what bearing you have by taking off the 4-bolt front cover so you can see the input gear bearing.
Good luck, post up if you have questions. If you need more detailed help you can pm me and I’ll try to walk you through it to get the details sorted. I recently learned all the ins and outs because I had to figure out if my 94 was new or old style before I bought parts for it.