Jim,
In my opinion what you don't want to do is do this twice.
It sounds like you want install the dual MC & bracket, split the lines, install the RPV's for the drum brakes and then later convert to disc brakes with a booster, etc. You would have to undo much of the previous work to accomplish this task. The disc brake MC/booster, brackets, prop valve kits generally come as a unit. While you have the MC you would have to get the bracket and the other components separately. I don't know who sells them that way.
I just did a 59 for a customer. We bought a kit (rotors calipers, bearings, booster/MC, etc) and everything bolted on. Had to purchase a couple of lines and some bolts separately but that was it.
Fred
