GM 1/8" hard plastic vacuum line used to be available at most good auto parts stores. You could use rubber vacuum line to replace them, but its bigger diameter and harder to route under the dash. All other vacuum lines under the dash are hard lines, with small rubber connectors on each end to connect to the vacuum motors. The hard line under the dash runs over to the controls and connects to the vacuum port. Hard vacuum line will slip inside of a small diameter rubber line, so you can make the transition at any point. I think the line through the firewall may also be hard, line but I don't remember for sure. The vacuum lines under the dash are GM "hard" plastic vacuum lines, not rubber lines. The second connector has a vacuum line running over to and through the firewall. It could be connected to either the carb or directly to the intake manifold. One connector has a vacuum line running to the intake manifold vacuum port on the carburetor. There are two vacuum connectors on the bottom. In my truck the ball is a larger cylinder, and it is mounted right next to the HVAC plenum under the hood. Without the ball, whenever you accelerate the vacuum will drop and all the HVAC doors will go back to the non-vacuum position. It will work without the vacuum ball, but the ball is the vacuum reservoir that keeps the vacuum steady. However you should measure vacuum at two of the vacuum motors when controls are in the Defrost position. I can't quite figure out the color of the vacuum lines connected to these two ports and what vacuum motor they run to, since the table on the right side has "defrost" listed twice. This means that if you put the controls in the Defrost mode, you should measure vacuum on Port 3 and Port 4. If you follow those lines with the word "vacuum" back to the left you will find that they line up with "Heater Mode"(port 3) and "OSA/REC"(Port 4). Then follow straight down and you will see the word "vacuum" on two lines. If you look at one of the control positions listed across the top, for example "Defrost". These are the same lines/ports that are listed down the left hand side of the table. There are five vacuum lines coming out of the back of the controls (lower right shows all the colors). There are nine ports on the back of the controls, but only five are connected. I believe this is what it it trying to tell you: That vacuum diagram and table is even more confusing than the one for my '75.
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