Has any 1 set up a 8 3/4 rear end with used gears ? I heard it hard to get them installed right. NO NOISE

Yes. Have rebuilt the cone style as well as the Dana Powerlok (clutch pack) type. What I have found is that if all I am doing is rebuilding a known assy (one that wasn't totally shot and did not make noise prior to dis-assembly) then I can replace the bearings and set it back up using the same shims, set the lash and the unit will turn out nice. This worked well for me with the cone style rears. I have messed with the powerloks too. I have not had the same luck with them. I have set them up with gears that I believe were original to the unit as well as installing used gears from another assy on a powerlok unit. With the powerloks I have not been able to put one together that doesn't make noise. I worked on one of them for hours getting the right shim stack up and contact pattern, lash etc. It made noise. I am about te embark on a rebuild of a 489 case, cone style sure grip that has never been rebuilt and am hoping that it is not worn out and can be made to run tight and quiet.

I haven't had much luck setting up used gears without noise.
I think once the gears are broken in, the only way to reuse them without making noise is to set them up with the exact pinion depth, backlash and preload that they were broken in with.