Positive Cab Ventilation

[AcampoDave]

A while ago while in the junkyard, I noticed that more modern pickups have oval shaped air check valves in the back of the cab below the bedline. Apparently, they have some kind of a flapper door to let the incoming air from the ventilation system escape thru a grated cover.
Has anyone ever tried installing these on their classic truck? It seems it would go a long way to improve the air flow of the heater and kick panel vents and I surmise it would reduce the wind noise when cruising with the windows up and vents open.