1978 Chevy Truck Interior Vent Controls

I'm new to this 78 and a kid owned it before me so no telling what’s been altered. I've installed a new A/C system which blows on the floor only. I'm interested in knowing about the controls for the venting to direct it through the dashboard vents. I've been told to check to see if there are vacuum lines going through the dash. I've found several lines plugged at the carburetor so I suspect there should be something going through the dash but I'm not sure. A diagram of the vacuum lines would be helpful as well as a diagram for the controls and cables on the dashboard levers. I have other repairs to do so I might be interested in purchasing something or a subscription to your service professionals since I'm really a novice and I appreciate knowledgeable mechanics as long as the price is right. I'm a 100% disabled Vet so money is a finite commodity in my life.