Splines in a 9" rear end????

http://www.kevinstang.com/Ninecase.htm

if it still has the factory tag
http://www.ridgenet.net/~biesiade/Fordrears.html

----EDITED FOR CORRECTNESS----

All 9-inch flanges have 4 holes, the small ones are closer together than the large ones.

Best way to determine the ratio of your gears are to count the teeth on the ring and the pinion.

Edbert said:

All Mustang 9s came with 28 spline axles.

Click to expand...

that is incorrect info. MOST mustang 9" rears had 28 spline axles but not all. drga pak cars and some regular cj's got 31-splines, most if not all boss 302's got 31 splines all boss 429's got 31 splines all boss 351's got 31 splines. a lot of the 67-68 shelby's got 31 splines etc. there were even some other odd-balls as well, i believe pretty much anything with 3.89/3.91 gears and lower (higher numerically) and any kind of locker also got 31 splines, this only applies to 67 up as far as i know, since i'm not a 65-66 expert.