FYI, those cars did tap into manifold vacuum. They had an accumulator with check valves so that the wiper lid and light covers would work after the engine was off (at least a few times). Vacuum lines are always rotten on these cars. Also, as I remember on the 69, the 70, and the 72 that I had, the switch for the actuation was a vacuum switch (the vacuum hoses ran to it). Check out a vette part supplier.

Test the operation of the headlights with a quick rerouting of the hose to a hand held pump or the engine manifold.

Dont replace just one vacuum line.....they all are rotten if one is.