I am unfamiliar with the drum brake setup. My baer brake kit is calling for Drum brake spindles and I am sure I reuse the hub in some way as the baer kit is missing the hub part of the rotor.
---the following is speculation here---
This being said, it looks as if the factory discs bolt to the backside of the factory hub. I was thinking that the factory drum probably sleeved over the front of the hub lubs similar to how the rear drums slide over the rear lugs to the axle hub.
Then I thought that if this is true that the drum brake hubs are probably different than the disc brake hubs.
Unlike many newer brake designs where the rotor is a separate component from the hub, the '67 rotor has the hub attached to it by the wheel studs that are pressed through the hub and rotor. You can separate the two only by pressing out the lug studs. I'm unsure whether the hubs are the same between disk and drum, as when ever I bought a new disk the hub came with it.
Tom (Johnson) Kubler, a.k.a. 289fan, HiPo289fan, TJinSA, Fy A. Thyrio, & various other unmentionable names.