Wow, that second website had an article that`s got a couple things that are just wrong or don`t make sense. First, the B-body rotor/hub assembly cannot be used on the A-body because the A-body spindle is too short.
The second thing that is not accurate is that the Mustang rotors would not work unless the outer bearing groove and grease seal are both recut and the rotor turned down in diameter. Who would want to redrill the rotor when most people want the 4.5" bolt circle? That article may have done more harm than good.