Bonanno's number one since Vito Genovese fall, and the later Genovese crime family leaders made efforts to get away from narcotics. The Lucchese were also big in it, which help the FBN grab some informants from that family.
Today it would look like this.
1. Bonanno
2. Gambino
3. Colombo
4. Lucchese
5. Genovese ( they would be higher on the list if we are only talking about financing narcotic shipments)
How come the Colombos haven't been caught up in a recent drug related case though ? I know that a Colombo member and/or associate got busted recently , but IIRC it wasn't related to drugs and the Colombo family as a whole has stayed out of the limelight recently , certainly with respect to mass indictments .
The Genovese family hasn't had any of its members busted for drug trafficking in recent times either , though Rooster Onofrio does have at least one past drug conviction .