Here ya go...Carter BBS. Kits and whole carbs are available. This carb has a good reputation.
The screw is hilarious.....there was a similar question a week or so ago about an extra hole in a Holley 1920....There is not any hole in the original carb where that screw is inserted in any FSM illustrations that I am looking at for this carb. The vacuum advance fitting is above there on the body of the carb where your last arrow points; it is ported vacuum. That added hole locatoin would give a modified 'sorta ported' vacuum; it is right above the throttle plate, at the level of idle transition slots. Yep, plug it.
They might have a rebuld vieo on this site; they sell your kits and the carbs.
http://www.carburetor-parts.com/Carter-BBS-Carburetor-Parts_c_152.html
