XJ
 

Are all XJ spring bolts the same size? Or does it differ depending on year or other reasons?

If you are referring to the bolt that goes through the spring eye into the XJ uniframe, and the upper shackle bolts in the rear, they remain the same over the years.

I believe it is a M14/2.0 x 120mm bolt. Flange Head. I don't remember the smooth shoulder portion length though.

Grade 9.8. Thats what the factory bolts have on them for my 97. Mopar part number for the bolts is 34202118. The nuts are part number 11502814 should you need them, which are welded in place.

All of the leaf spring and shackle bolts are M14x2.0 120mm ISO Class 10.9 with a flange head. If you can't find those, you can use a suitable hardened washer (must be Class 10) or a similar SAE Grade 8 washer. Or your local dealership might have them for a reasonable price (mine didn't)