Lincolns! Well compared to the Lincolns a G20s system is no sweat, no swear!
You're correct, other than the vacuum operated power brake booster on some models, the engine vacuum on a G20 is used for the defrost, floor and dash air dampers to direct air flow, the water control valve to the heater core and some of the emissions controls. The temperature air door is via manual cable. (unlike the automatic systems on those Lincolns)
The older models, if so equipped, used engine vacuum for operation of the cruise control as well. But that's it.