The part number is for the metal washers that go to the top of the shock. So in this order starting with the shock removed from the mounting hole: metal washer, bushing, insert shaft into shock mount hole, bushing, metal washer, top nut. You'll only use 2 metal washers per each side on top.
For the bottom shock mount where that bolt is that goes into the stud attached to the diff, I just reused the washers from my 5100's. Hopefully this makes sense. If you want I will be happy to take some close up pictures later on if you want/need me to. Just let me know. I remember you specifically asked me a few months ago about the washers and I wasn't 100% sure at that time.
So you didn't use a centering washer on the shock shaft where it mounts to the frame up top?