Thanks to that website about cars used in movies I discovered why the original DVD listed Connie's birth year as 1927.
They apparantly based that date on the car in which Vito and his family drive when they first returned to Sicily, as that car apparantly is a Fiat 503 Torpedo from 1927.
However, according to The Godfather Legacy and Godfather book it was 1922/1923, apparantly based on Coppola's personal notes.
If you look at the little boy in Vito's arm (which is Michael) I think there's now way he could have been older than 4 years old.
What do you guys think?
