Using mustang rotors for 4.5" bc

I called SSBC after I saw this. I have KH disk on my '67 FB. The guy told me in order to use their rotor's I would have to change my spindle's out to 10" drum spindles. Then my disc brake caliper bracket's would no longer work. I would have to buy their's. You can still use your caliper. It create's a domino effect.
I think it's best to stick with longones idea. I just need to find a Machinist.