12 bolt chevy 273 open rear that was in my 67 GTO when I bought it. I believe it is the second generation rear end for 1968 - 1972. It does fit earlier applications but is 1 " wider that the 1964 - 1967 rear ends. I can not find any codes on it. Rear is complete from drum to drum with brake hardware and e brake cables. Was in a running driving car until pulled a few months ago. Housing is pretty clean with very little pitting. Great rear to build. Rear is approximately 61" from outside drum to drum. Would consider trade for a running Buick 455 $450 obo IL http://chicago.craigslist.org/nch/pts/1969708826.html