Best Carb rebuild kit

Certainly not a Holley 1920, nor Carter BBS, so must be a Holley 1945 & looks like one (I never had one). You can find a manual on-line I recall. The "list#" is usually on the air horn at the top. The step cam is normally a bit "loose". I don't see any obvious parts missing. I think many had the open cavities at the top. Later, they added a plate w/ a hose to a charcoal cannister, perhaps for CA cars only in 1974.

Check that the choke pull-off's diaphragm isn't torn. That is the part at the bottom, left or your 3rd photo. Use a hand vac pump or just push it in and block port w/ your finger and see if it holds in.