Fresh Air Vent Vacuum Actuator

[CS10]

Hi,folks I am new to the sight and having problems with under dash vacuum lines and actuators, I need a new actuator, the one located under cowling on passenger side of vehicle original one rusted won't work, also need to locate new small plastic vacuum lines under the dash old ones deteriated and spliced with I/V tubing. How many of these actuators areon the truck and where are they all located? I also only get air thru defroster and on floor, I have already replaced vacuum hoses in engine compartment and replaced vacuum switch on climate control on dash.
1989 S10, 2.5 Liter Engine, with A/C and 5 speed manual trans.
Any help, Info, and Advice would be greatly appreciated.
Thanks in advance, CS10