The episode has The Godfather still being filmed and Joe Gallo being assassinated in retaliation for his arranged assassination attempt on Joe Columbo. This takes considerable liberties with the timeline as The Godfather was released in theaters on March 24, 1972 and Joe Gallo was assassinated on his birthday April 7, 1972.
Joe Gallo's murder on his birthday on April 7, 1972 happened a month after The Godfather was released in theaters. The murder is depicted in the episode as during filming in 1971.
This episode indicates that Ruddy had the finances to send the crew to Sicily, because he didn't have to pay off Gallo, because Gallo was killed. This couldn't have happened. The Godfather was already in theaters in March of 1972. Joe Gallo was killed in April 1972.
When mobster Joe Gallo is shot inside Umberto's Clam House, it is clearly daylight outside and he collapses onto the floor. In reality, "Crazy" Joe was shot soon after 4:30 AM. It was still dark outside. And, though mortally wounded, he was able to stagger to the front entrance.