The Don Is Dead (1973) on Netflix

Plot summary

Frank Regalbuto, the ambitious son of the mafia don Paolo Regalbuto, sets up a heroin deal with Tony Fargo and Fargo's brother Vince. Someone inside the rackets tells the police, and the deal turns into a gun battle that Frank and the Fargos barely escape. Frank then hears that his father has died of illness, and the mob families meet to choose a successor. They judge Frank too young to step into his father's role, so he will learn the trade from Don Angelo DiMorra, a lifelong friend of Paolo, who takes on the job of protecting the man meant to be the next don.