Question about vacuum hoses.
You should have a vacuum fitting that is screwed into the intake manifold.
How many nipples are on the fitting and where do the hose or hoses go from the fitting.
Didn't the 1974 models have vacuum hoses connected to the egr valve,temp sensor on radiator, vacuum amplifier, etc.
The manifold vacuum nipple has 2 outlets, one smaller than the other. I'd have to check to be 100% sure, but I believe that one goes to the HVAC vacuum reservoir and one goes to the vacuum amplifier.