1bbl slant pics

Appears that both old & new are a Holley 1945. I have the manual, but it shows only an early one like your bottom photo and a later one w/ electric choke. It doesn't show the hole w/ adjustment screw. I wonder if there was a special "clean air" one for CA.

The vent tube went to a charcoal canister. Definitely on 1974 CA cars, not sure about other states. You can find rubber end caps, otherwise a short piece of hose w/ bolt in the end is a redneck fix. However, I don't know that just capping it off will work since I think the float bowl should be vented at idle. Earlier carbs had a vent hole with a rubber disk on lever that opened at idle.