Not sure if this is helpful but I have had several cars over the years have their rear diffs rebuilt by Jim Rowe at Metric Mechanic in Rich, MO. For me, always quality work and no complaints. Reasonable turn around time. He is currently building a 3:45 60% LSD for my 1973 e9 CS.
One of previous owners had a repaint in 2003 and painted Anthracite Grau with tan interior. I am taking back to original color and trim : Ceylon Gold with Black interior. Building a M30B34 bored to 3.7L with 50mm ITBs and fuel injection, headers, 5 speed conversion , etc. Should produce somewhere close to 300hp. I plan to post lots of pics when I am finished. CAN"T WAIT !!