I have searched the forum, looked at the data page, looked at other sources, but I am confused. I just purchased a rear end and I was told it was a 3:42 posi, but not specific as to what it came out of. The seller took it off a 78 Camaro, but he built that car from several cars. The stamped number on the axle tube is a 2 (maybe..really chopped off and offset) followed by PY G314 1 The cast part number is 1254333, it also has what I believe to be the date stamp K68 Another cast number GM30 It SEEMS to have been produced in 1978, but the stamped axle code is missing the posi code (after the PY G314 1) I found information that the PY code was used on some late 70s Firebirds, is this what I have? Ultimately, how can I find out if maybe somewhere along it's life, someone changed out the gears and differential, and just kept the housing? Can someone help, and maybe post pictures of what a posi vs an open diff look like?