Um silly Question about factory A/C air

[tphsmith]

I have nothing to refrence and the FAQ's just didnt hit on this topic as I could find so here is the question. under the hood on the fire wall there is an assembly for the cowl vent. keep in mind this is while standing in front of the grill facing the windshield on the left side of the firewall above the evaporator housing there is a arm post that connects to the actuator. and now if you are on the passenger side inside the cab on the fresh air vent in the kick panel there is an assembly on the fresh air vent connecting to a actuator. so my question is now that i have located these 2 locations on the truck in the (assembly bible) factory assembly instuction manual. the question is are thes both needed or is the one on the fresh air vent an option if you dont have the one mounted on the firewall