What PDB booster and Master for 71 Demon 340?

That looks like the later Bendix, 73 and later. Note the location on the check valve. 72 and earlier uses the Kelsey-Hayes, see my posts 4 and 5 above. As long as it is the dual-diaphragm disc unit, I believe it will work. The drum boosters typically are single-diaphragm. Someone correct me if I'm wrong.