Let me know what solves your noise problem with the reverse.
I have had that noise forever and when I changed differential fluid I didn't find any metal shavings in there just a dark brown fluid..

 

Just figured I would mention that when I got the new axle in, I opened the diff on the one I blew. The pinion looked and felt like it was meant to be smooth. the ring gear got a few blades damaged, but nothing compared to the pinion. Also to note: my blazer has over 200K miles on it. I did the axle swap with hand tools, although I did but a breaker bar (the kind with ft/lbs on it) for the ubolts on the leaf springs. Getting the old axle out after being disconnected was a lot harder than getting the new one in. I didn't even scratch my American flag painted diff cover. that shocked me. This was a great time to redo brakes as well. However, my parking brakes wont fit in the rotor. weird.

 

I believe the A-arms are mounted differently to the frame and are a ZR2 item only (different ball joint location for wider track ) like the C/V shafts. The ZR2 front differential came with special factory heat treated gears in a 3:73 ratio only. I will be swapping both after rebuilds, I got a fantastic deal on them I just couldn't pass up !