I have an '86 GMC truck that originally had A/C. Many parts were missing when I bought it. The fan blows but I can't switch between the different vents because the vacuum lines were disconnected when a different motor was installed. Does anyone know where I can find diagrams or information that can assist me in getting the vacuum set back up? I installed a Jegs vacuum reserve canister to assist with the brake booster. The motor has an aggressive cam so I don't get a lot of idle vacuum. Does anyone know how much vacuum it takes to run the A/C duct work?