Using mustang rotors for 4.5" bc

So I decided to convert my car to 4.5 bolt circle and bought 2 Raybestos 6004R rotors. I was looking at the seal cup on the Ford rotor and most all of it will be milled off to match my Mopar rotor. So if the bearing race diameter's are the same why can't you just slightly bevel the Ford race dia. to match the Mopar race dia. and tap in the Mopar seal? Then you have the correct seal for your car.

If I'm missing something let me know. But it looks like it would work.
I took them to a machine shop and he wanted $300 to cut them. Need to find someone else.