87 NA Differential

Who rebuilds NA diff. in the NC area? Mine is very noisy and I believe that the rear clunk that I'm hearing is coming from it. I have replaced all of the bushing, rear diff mount, and drive shaft u joints. I can hear the clunk when I put it in gear and when I give it gas at low speed or when I pat the gas at low speed but in a higher gear. It sounds like a clanking noise or a metal to metal clunk!!!