i have a few questions... one, i have a 1969 mustang with a 302... so do i have a 8' rear end or a 9'... and also i was under the car and noticed a tube coming out of the differential going up in to the car... what is that

 

Probably an 8", unless changed by a PO. The tube is a vent.

 

quick ref for 8" verses 9". . . . . and 8" center section isoval (flat on the bottom/top), and a 9" is round.

 

The 8" and 9" look very similar and depending on what it came out of some look more round (in both the 8� and 9�configuratios) and some look more oval. The “for sure� way to tell is to try and stick a socket and ratchet with extension on the bottom bolts. If you must use a wrench with one of them it is a 9" if socket fits on all the bolts it is an 8"