Kelsey Hayes replacement rotors question

Hi - I have obtained new brake rotors for my 69 Dart kelsey Hayes disk brakes.The problem is the diameter of the replacement rotor is slightly larger than to factory rotor so the rotor doesn't sit tight on the hub, even with the wheelstuds pressed in. Just wondering if anyone else has run into this situation and how to correct it? Would prefer OEM rotors but hard to come by.
Please advise,THanks Chris