That's an 8" rear end. A 9" would have a hump on it. Here's some information you need to read to give you the whole picture. http://www.kevinstang.com/Ninecase.htm
"Later improved carrier for the 8" found in 67 and up
Note the presence of fill plug, and that the casting number is moved to the outside of case, while other previous 8 and 9 inch carriers it has always been on the inside.The number here is the familiar C7OW-4025-A. "