I don't recall "ever" seeing Detroit being heavily involved in narcotics trafficking. Not saying nobody dabbled, but I would venture to say that Jack Tocco wouldn't have tolerated it as they really focused on traditional LCN crimes and were heavily involved in union infiltration.
The Gametax indictment confirms they dealt in drug trafficking. And I'm almost certain the Nove Tocco & Corrado tapes mentions something about Jackie The Kid wanting to tax the drug dealers, along with the bookies, and loansharks.
