Ford rear end

I would rebuild the one you have rather than replace the whole thing . You can always change the ratios for what ever kind of driving you like , especially if the tranny has over drive as long as the computer is good with it . It's usually best to go with how the vehicle was designed .

You could also check the metal tag on top of the axle housing. It will state exactly what ratio you have. There are tons of PI's in the bone yards though, getting a used rear end should not be a problem. A pre 2006 PI would most likely have a 3.27:1 ratio. Just pay attention to the SPLINE count! 31 versus 28, 31 would be on the newer rear ends. Midwest Mustang sells them online dirt cheap.