I was looking under my car yesterday and was wondering how I can tell if I have an 8.8. It was about 8.8'' across so I'm guessing that's how you tell? Thanks. (I have a V6 btw and I know they don't come stock that's why I was wondering.)

 

The shape of the pumpkin, I attached two pics from american muscle just look at the bolt pattern of them. Also, if you are doing one wheel burnouts then you will have the 7.5.
http://www.americanmuscle.com/frpp-88-diff-cover.html
http://www.americanmuscle.com/mustang-v6reargridle.html

 

Damn... lol