I was asked to decode what was supposed to be an original rear of a very original 1972 "SS". What puzzled me from the start was that he said it was a 10 bolt and not a 12 bolt. It's my understanding that all big block Chevelles had 12 bolt rears.

Here are the digits he gave me:

Casting# 3917123
Stamped on the forward facing pass axle tube FJ O929B


Thanks.

3917123 is a 1968 Chevy 10 bolt. FJ is a 3.08 ratio. 0929 is September 29, and since it is a 1968 model housing it would have been cast and assembled in 1967. The housing has obviously been replaced at some time.

Bruce

Thanks Bruce.