Using mustang rotors for 4.5" bc

Ok solved the problem some are having with the rotor not fitting with the dust shield in there. The problem is the original landing for the mustang grease seal needs to be milled off and you'll have plenty of clearance between the rotor and the dust shield.

Now my question is: is the the outer diameter of the original Mopar seal the same as the outside diameter of the bearing race? If not, does anyone have the outside diameter of the Mopar seal?

It is very close to the same. I just took a die grinder and beveled the seal seat a little just to get it started in the bore. Look at your old Mopar rotor, it's the way the factory did it.