Mustang wheels seem to be a common go to when moving to 18’s so I don’t know if there is a need to push the wheel away from the caliper more. It’s worth keeping in mind. The benefit of the Mustang platform seems to be availability of calipers and the opportunity to go bigger. Could probably be just as simple with SRT goods but my recollection is six piston SRT calipers are quite a bit more money than six piston Mustang calipers. I could be wrong though. We probably need to pick a platform and roll with it, then work on geometry.