See if you can find a shop that's involved in round track racing.(NOT drag racing!) The roundy-round guys have to know what they're doing where final drives are concerned, because they have to function properly on both pull and coast, repeatedly, under full throttle operstion. Setting up a rear end isn't rocket science, but there's virtually no room for error. Getting the preload, pinion depth, and tooth contact pattern is vitally important for long life and quiet operation. Wish you were closer to Nashville, I'd be glad to help!
Jerry
