I was thinking that McGurn was Taylor Street because Rio, Ricca, Volpe and DeGrazia all lived near each other. Another reason -- this is just speculation -- is that Rio may have been McGurn's protector, and that after he died in 1935 Campagna and Ricca took him out.

Agree that McGurn was Accardo's "Chinaman" as you put it, but wonder if he was moved to a different crew after Capone was put away.