I got a good deal and need advise

Here I thought the package deal was worth it because of all the extras I got with it. Didn't realize traction bars were tabo on a mopar. Even got all the brakes with new hardware and drums. and custom axles with small bolt pattern.
Is there something I need to look for before I install the rear. How would I check the sure grip unit? It is the clutch type sure grip and as far as I was told it worked well, but the guy wanted a better set up. He said he switched to a posi traction unit. Different from the sure grip. Any way, When I turn the pinion back and forth, I can hear a slight clicking between the pinion gear and the ring gear. I guess this is called backlash. How much is too much?