Giovanni 'John' Bonventre was a Bonanno underboss from 1931 to
1950. It is speculated that Bonventre died sometime in the 70s.
Does anybody know the exact date and year?

John Bonventre was an uncle of Joe Bonanno who came to the US in 1933. So he was one of those few guys who were made into one of the five NY Families during a period when the books were officially closed. He was a captain though, never an underboss. In 1940 he was demoted by Bonanno after he had somehow offended Stefano Magaddino during a dinner party. However, Bonventre was upped to a captain´s rank again four years later. He retired to Sicily in 1958.

I know he was born in 1901 but have no clue when he passed away. His date of death can not be found on the usual researching sites like social death index etc. Perhaps Faith would know Bonventre´s year of death?

I don't know either. As far as I know, Italy doesn't have anything like a Social Security Death Index to look up when people died.

There is no such thing as a social security death index in italy. You'd have to fill out a Death Certificate form (in Italian only), send it to the town where the person died along with necessary fees, etc and they'll get back to you.

edit: and you need to provide them with all necessary genealogical info, like his parent's names and grandparent's names and if even one name is misspelled, back to the beginning you go.

I read somewhere the last 70's

Yeah... About that...

John Bonventre was never an underboss. He was capo in the Bonanno crime family. Vito Bonventre was his brother, his nephews were Joe Bonanno, Joe, Salvatore, Frank Profaci, and Cesare Bonventre. He had some legitimate business in Vermont as well as having a soldier in his crew having a bookmaking operation in Vermont. He died on Filicudi in the late 70's.