I am confused as to what year rear end I have. I am Not sure what vehicle it came out of. Every chart I have looked at is not helping, here are my measurements: inside flange to flange, 55 3/8". Perch-perch center, 46". Axles, 30 3/8", open diff., 742 case. Every measurement gives me a different year and body. my measurements were taken with my trusty tape measure . Any help?