Not sure what you mean by south building, but the BWV rooms right next to where the elevators are end in 66, 68, or 69, and those ending in 70s are fairly close. Go to the room maps in this thread https://www.disboards.com/threads/bwv-room-view-and-number-maps.3794835/ and particularly view the ones that show the elevator location and rooms nearby in BWV Luna Park Pool (2) and BWV Driveway. And although the particular room map does not specify the location of the elevator, the elevator is close to the pool/garden view studios ending in the 50s on the left side (when facing the map) of the BWV Courtyard View page of the maps.