I came up with this by painstakingly reviewing every one of these drawings (link below) trying to find a rotor that matched the basic dimensions of a 67-70 disc rotor but also would have an inner diameter large enough for the 65-66 drum hub to fit inside it. Unfortunately I could not find one that had a 5 on 5" lug pattern, a 3.050 register hole and was roughly 2.90" in height. The Ram rotor came closest but its lug pattern is wrong and it requires lathe turning the drum hub.
If anyone is aware of a better rotor choice, the basic dimensions to match are: Outer diameter of 296-300 mm, Height of 74-76mm, 3.05" register, and has a 5 x 5.00" lug pattern. Friction surface to be somewhere around 1.2" thick, and vented, of course.
Additionally, an inner diameter of 6.4" would making lathe turning the drum hub unnecessary.
https://brakeperformance.com/images/.../brake-rotors/