1966 273 afb

Hello. I have a 1966 Formula S with the "Clean Air Package" (CAP). The carburator is a Carter AFB 4120S (stamped on the base - it has no tag). My question is: What is the difference between the regular AFB and CAP?

The engine has a breather on the rocker cover on the Drivers side that has a hose that goes to the base of the Carb - I believe this is the PCV. The other rocker cover has a breather that has a hose that goes to the outside cover on the air filter. Is this different than the "regular" 273's (not CAP)?

I am sure the carburator needs to be rebuilt, it has been sitting for 10 or so years. I don't know if it would be best to rebuild it or get a new one (like an Edelbrock - I see them on e-Bay for ~$150), but I don't know which model to get.

Thanks for your thoughts.