Look on the housing, and see if you can find a code. My guess is ...it is KQ, as I have an idea about your car. Anyway, the M-22, which was in you car, was a heavy duty option, and the rear probably was the same. The racing angle probably was the reason for the M-22, and thus my guess about the rear coding probably is correct. If it isn't that code, look for a KK code. It is 4.10 posi also.
For all who are interested, KQ was a 4.10 Posi, H/D rear installed in C.O.P.O cars. I think his car probably was one in the beginning, but is missing the engine, and tranny. The car had a interesting history, racing up in the north west from what I recall you saying.
The count is 9-37, as you stated above.
So, how you been lately? Got that car finished yet? Doug