Using mustang rotors for 4.5" bc

I picked these up from a buddy who went to drums. He is the real deal old guy drag racer. Very involved in the sport. I have no clue how it was done. I was at his place visiting, he showed me the car, and said for a song I could have the K/H setup. I sang. I can take a closer look at them.
Thanks for the response, I actually meant to ask Perfacar, my bad. Why didn't you use them?