I paid $250 to have both my diff's setup with a soild spacer in the rear.
However you get what you pay for.
I had to pull my rear diff due to really really bad backlash from them not setting the rear diff up properly.
They claimed it was from the front pinion bearing shims falling out of place from me changing the front driveshaft flange.
My backlash sucked to begin with after the inital 500 mile break in.
It sucked even more after I changed the leaking grooved differential flange. However I think they didn't put a soild spacer in to begin with and that's why.

I spent $75 for a junkyard 4.10 diff to throw in temporarly and a 4 week wait without my rear 5.29 diff which I just now got back on friday.
I do know now it has a soild spacer in it because I stopped by to check on the progress. They were installing the soild spacer which looked brand new and they claimed they needed to order some new shims for it but whatever sounded kinda shady to me....