I believe there is a mod you can do with Mustang rotors. Mustangs used a KH brake setup from the factory and had a larger bolt pattern. You have to machine the inside of the rotor for the Mopar sized bearings I think. The Ram Man was offering this service at one time but it was pretty expensive. I would not deal with him. I know there are posts about this on FABO. Maybe do a search there.

Also, I believe Wilwood sells a conversion kit that uses the stock drum spindles. This might be the large bolt pattern. Not sure.