As a side note, what about the carb bowl vent line and the vac and purge lines on the carbon cannister?
Somewhere, in the FSM, I suspect there are vac hose routing illustrations for both the HVAC system and the emissions system too.
Typically, the vac source for the HVAC system is a vac tree on one of the rear intake manifold runners or a fitting on the power brake booster's main vac line, at the booster. In some cases, there might be a separate vac reservoir under the hood, where the HVAC vac goes first, before the vac goes to the control units. That additional reservoir can also have a check valve in it to prevent the a/c air from coming out of the floor and defroster vents during long periods of heavy throttle and lowered intake manifold vacuum.
Just some thoughts,