There is actually a size difference for OEM half shafts.
Some Troopers were assembled in Taiwan, not Japan. The Taiwaneese Troopers used a shaft with a smaller inner cup.
Now, we are talking about someting from 20 years ago, so who knows what is under anything you find in a junk yard. Thre are plenty of vehicles that do not have their OE shafts under them.
Then, there are reman shafts. As long as you replace the entire shaft, it is not a problem. It is when you try and replace the outer half-shaft by leaving the inner shaft installed in the front axle housing.
Also, with remans, there are also shafts out there with a tripod joint for the inner joint. Instead of a race and balls, it is three pieced yoke with rollers on the ends that fit into a corresponding cup.
In the end, you really can't tell until you have it apart and have the parts side-by-side. Most of the time you can swap out the race/balls from an old shaft and put them on the end of the replacement shaft. This prevents having to disassemble the front end. But...it is up to you and up to the condition of the your joints.
That said, I would not sweat the OEM vs. non-OEM thing too much. I would suggest either cleaning and rebooting your shafts, buying a shaft from a JY or an auto parts store. You will need to regrease and reboot both the JY shaft and your own. The one from a parts house will be ready to go and it will most likely have a warranty. The choice is yours.
Good Luck,
Michael
