1967 Camaros had a least two different type of AC controls. I've attached a copy of Page E8 from the Assembly Manual and Page 1A-80 from the Chassis Service Manual to show the difference. The Assembly Manual revision shows that the control was revised on Feb 1, 1967 so your April build Camaro should have the second design control functioning with the diagram in the Assembly Manual. The main difference is the elimination of the Blower Switch in the second design. Both systems use the Compressor Switch.
The Compressor Switch is a vacuum electric switch used to turn the compressor on and off with the logic (geometry) of the Heater AC Control lever. This logic was used throughout the Chevrolet and GM line of cars. The Camaro system being very similar to the full Chevrolet line. The main advantage to this system is that the compressor can be cycled with the logic of the vacuum so that the air conditioning air doors in the cowl and passenger kick panel work with the temperature doors. To make this work there is another vacuum control mounted in the main control which works off of the control lever to cycle the vacuum to the appropriate location. This is shown in the diagrams.
The Compressor Switch is normally closed so a failure in the vacuum supply turns the compressor on if it is supposed to be off. There is also a vacuum canister with a check valve mounted on the firewall to the left of the steering column under the fender that supplies vacuum under low vacuum conditions so that throttle position and load to not affect the operation of the system. The Compressor Vacuum switch can be a problem due to the rubber parts that are old by now and usually crack and leak as you have found out. This system was eliminated for the 1968 year in favor of an electric switch mounted on top of the air distribution box under the dash. This works on a cam system based on air door position.
Hope this helps. If you have any other questions let me know.
Blake
