It's probably due to c clip vs non c clip design.
Depending on how much new spiders cost I would just swap to an 8.25. At least around here they are approx. $100 at the junkyard, $50-100 on the forum classifieds, and all you need to swap to one is an appropriate driveshaft and set of U-bolts.
The driveshaft is easy to find in the yard, factors that affect length are 4x4 vs 4x2, auto vs manual, 4cyl vs 6cyl, and 95 down vs 96 up. You would want one from a 95 and earlier with the same drivetrain as you.
That being said, the part number I see for you is exactly what Tim listed. If you had a 90 apparently it would be 5252 495. Either one is a full set including the cross shaft, thrust washers, and spiders/side gears plus the cross shaft retention bolt.
edit: it is definitely c clip vs non c clip. I'm fairly certain a set of c clip gears will work for a non c clip diff, there just isn't a c clip to install, but for a 90 or later one would definitely need the later part number gears.