So I've hit a wall with my build. I thought I had a possible 57-64 9.3 Pontiac/Olds rear end under my Thunderbird, but now I'm not so sure. I found what looks like a production date code on the 3rd member, but I'm having hell finding a way to decipher it. The code on the side is J316. From what I've been able to find online, the last number designates that the 3rd member was made in 1956. I want to say that the J is a factory designation for October, but I could be completely wrong. If the information I found is correct, this means my differential was made on October 31, 1956. This tells me absolutely nothing because I have no idea when GM started producing the 1957 Oldsmobile line. All I know is that my rear end was made in 1956... Could any of you help shine a light so that I might climb out of the darkness?