Using mustang rotors for 4.5" bc

I picked up a pair of mustang rotors to make this conversion on my 69 barracuda. After taking a lot of measurements it appears to me that the outside bearing will bottom out on the spindle before it preloads the outer bearing race if you move the rotor in by moving the inner bearing race in by 0.270". Based on the rough measurements that I've taken it looks to me like the outer bearing race needs to move out by about 0.130" to keep the distance between the two bearings similar to the distance between the bearings on the stock barracuda rotor. Anyone else run into this?