SSBC replacement parts

A year or so ago, I asked them if the rotors would fit a stock K-H system. I was hoping the rotors would be a cheap and easy way to convert to large bolt pattern. They replied right away, saying they would not fit.
If I recall, they used a rotor with a dual bolt pattern, drilled for 4" & 4.5". They shipped with one size installed, and the other one studs in the box. I'm not sure what machining would be necessary to make a Mustang rotor fit a Mopar drum brake steering knuckle, if indeed that's what they did.