Any Disc/Drum setup will require a Combination Valve (Metering Valve - Hyd. Safety Switch - Proportioning Valve) or the (3) individual components. You will also need/want the 10 PSI Residual Pressure Valve for the rear line. Last I checked they no longer came preinstalled in the Master. A power brake system is always preferred with disc brakes due to the required increase in line pressure, so if your going to run a manual disc brake system, you will need a small bore master to compensate. The only rub there is the fact that a small bore master moves less fluid than a larger bore, so pumping the pedal may or may not be necessary depending on how tight your drums are (having a residual pressure valve helps there).
A factory disc/drum brake '71 Charger would have a 3pc valve set up....A proportioning valve, the distribution block and a metering valve (AKA hold-off valve). The Hyd. Safety Switch is incorporated into the distribution block and has a single wire that connects to it, and runs to the dummy "Brake" light in the cluster. A drum/drum '71 charger will be a 1 pc distribution block. Inline tube as well as Year One, Classic and others sells the factory stuff, if you're looking to spend the extra dough for factory style stuff. Like mentioned, using your factory distribution block with a plumbed adjustable proportioning valve to the rear will work just fine. There are many here that run that set up. Or, go with an aftermarket adjustable combination valve. Both options will run you well under $100.
Pretty much all Dorman, Raybestos, Bendix, Cardone or other factory style disc/drum master will have the residual valve built into the drum port of the master. I haven't run into one yet that hasn't. But, never the less, things could be changing, so check **see pic below**. The more flashy Wilwood, SSBC, Baer ect..ect... that have limited masters designed to cover a broad range of applications may not, being they're going with masters that could be used in a disc/drum or disc/disc application. They leave that responsibility to the customer and will be spelled out in the installation directions. Do not install a 10lb residual valve for the rear's if you do not know, especially if you're going with the more off-the-shelf factory styled disc/drum stuff (being they should have one).
Here's a clip from the FSM showing residual valve location and removal:
Bottom line is to contact your brake/caliper MFG. Without knowing caliper volume to figure out M/C requirements, one would be guessing. On a larger 4 piston set-up you may need all the way up to 1 1/8". Obviously someone chiming in that has a similar, well working set-up would be pretty nice as well. Also, depending on the route you go with the M/C, ensuring you're not piggy-backing one residual valve on top another in the same circuit needs to be squared away. Good luck.
