I also had one caliper not fit correctly and ground off the bump, the other side fit perfect, I now have 2 matching (bendix) calipers for the other conversion in the wife's 66 dart.
Also to for making the changeover easier I replaced my studs with the screw in type so that I didn't have to countersink the rotor in case I ever changed to a different type of rotor or ruined the ones that I originally bought to use with the scarebird setup.
Now I have the option of using either the 5 on 4" and drilling a rotor or the 5 on 4.5 by just unscrewing the studs from one set of tapped holes to the other set. I had the 5 on 4" SBP torque thrust mags on at first then went to BBP rally's because I just like the style better(after I find matching center caps that is).