I have just removed my rear end from my 67 coupe to put in new springs and want to change my wheel bearings before I reinstall it. I have a leak at the housing gasket as well as behind the u-joint yoke. When I went to Advance Auto Parts with the unit. they gave me a gasket that they said fit both the 9 inch & 8 inch units, but when I put the gasket aginst the bolt pattern the gasket was too small. They parts store then told me it was a 7 inch rear end and ordered the gasket as well as the seal behind the yoke. I'm left wondering if they are just out of the loop and should I order from Mustangs Unlimited but I am still questioning the size of differintial.