I put disc on mine. Wilwood can give you a rotor with 6 lug pattern for a 9".
I called Strange and ask for tech and a women answered the phone.
(this is usually not a good sign for me) I ask her did they have a rear disc brake with a 6 lug bolt pattern for a Ford 9". She told me they had 5 holes for a Ford, but I'll ask one of the guys if we can drill another hole in it. I thought (bad assumption) whoever she was gonna ask may realize what I wanted and help me. She then told me they could not drill an extra hole it! I just laughed hung up and called Wilwood and got my brakes within a few days!!