How about he got "Once Upon a Time In America" made sooner?
1964-A Fistful Of Dollar
1965-For A Few Dollar More
1966-The Good, The Bad, and The Ugly
1968-Once Upon A Time In The West
Starting Clint Eastwood as Harmonica and Henry Fonda as Frank (Hey this is a Alternative History thread

)
Also starts Natalie Wood as the lady
1971-A Fistful Of Dynamite
Starting Clint Eastwood as an Irish American that got caught up in the Ireland revolution while visiting his cousins in the old country. The irony being he was betray by the same cousin who convinced him to take part in the cause
Think of this sense but with Eastwood:
http://www.youtube.com/watch?v=ZXSofUNDcgs
Also starting Eli Wallach as the Mexican bandit
The movie is well know among fans for the re team up of Clint and Eli. Sadly, Clint and Leone had a falling out during production.
1974-A Place Only Mary Knew
Leone last western, the plot take place during the civil war where a Union Officer, A Southern con-man, A free slave, and an Italian Immigrate must team up to find the treasure while avoiding getting caught in battles. Mary was the name of the Con-man's dead girlfriend/partner, hint the name "Only Mary Knew"
Cast:
The Union Officer: Steven Mcqueen
The Southern Con-Man: Harrison Ford
The Free Slave: Sidney Poiter
The Italian: John Cazale
1977-Once Upon A Time In America
Leone's pet project since the late 60's. Based on the novel "The Hood" by Harry Gray. It Chronic the lives of Jewish ghetto youth who rise through organize crime during the prohibition. It took place during the 20's, 30's, and 1968.
Noodle: Robert Redford
Max: Paul Newman
Young Deborah: Brooke Shield
Deborah: Ummm no idea...help me out here
Winner of Five Academy Awards:
Best Picture
Best Director
Best Original Scores
Best Film Editing
Best Adapted Screenplay
1982-900 Days
About an American Army pilot (Harrison Ford) that caught up in the battle of Leningrad. (I know it was suppose to be photographer, but I think this would make things more interesting. And I have heard stories about American pow's getting caught up with things on the Eastern front). During the battle he fell love with an young female Russian Solider (Amy Irving) whom he impregnates. The movie focus the two fighting the war and avoiding the secret police because relationships with foreigners are forbidden
Academy awards:
Best Cinematographer
Best Sound Edition
Best Sound effect
1986-The Mission
Starting Robert De Niro and Jeremy Iron
(Yeah I know, but because of Ennio Morricone's score in the OTL let's just pretend Leone made this movie)
Academy Award:
Best Original Score
1987-The Last Emperor
Leone reunited with Bernardo Bertolucci (Who wrote Once Upon A Time In The West) to make a bio film about Pu Yi, the last emperor of China who was captured by the Soviets during the end of World War 2.
Academy Awards
Best Picture
Best Director
Best Art Direction
Best Cinematography
Best Costume Design
Best Film Editing
Best Adapted Screenplay
Best Sound
During the late 80's, Clint Eastwood and Sergio Leone reconciled and was planning on making Unforgiven together. Sadly, Leone passed away in 1989, Eastwood went on to make the film in 1992 and won Best Picture and Best Director. The Movie is dedicated in his name and Don Siegel