Ford at one time planned both vacuum assisted clutch and brake controls and went the furthest with the former, including submitting a patent application and eventually being granted the patent in either 1937 or 1938. In any event it was never released, even though all '32 firewalls have provision to attach the vacuum canister.
What originally ended up in that hole in '32 V-8 manifold such as in your photos was a slotted headless plug, not the fitting shown in your photo.