Been looking in to an IRS some more. The 99-06 Lincoln LS setup looks to be a viable option. They are plentiful and cheap. They were also used on the last generation of Tbird and Jag S type. They are only 61" wide, so no narrowing needed there. The suspension layout is similar to the 2002-2005 Explorer. You can even use the Explorer rear strut and coil spring on it. They have a weird 8" rear diff that can have either a 3.31 or 3.58 gearset. They don't have a limited slip option. The Lincoln and Tbird had traction control, so I'm guessing that's why. Digging through the parts catalog, the internals of the 8" are virtually identical to the 7.5 and 8.8, I'm guessing a 28 spline limited slip can be added without too much fuss. They do have the 5x4.25 bolt pattern, but Mustang Cobra hubs can be pressed on or the hub assembly and rotor can be re-drilled.
