IMDB - http://www.imdb.com/title/tt0064860/

I quattro dell'Ave Maria (original title)

After Cacopoulos (Eli Wallach) manages to save himself from being hung on a false charge, he robs Cat Stevens (Terrence Hill) and Hutch Bessy (Bud Spencer) of a lot of money and steals their horses. This results in a merry chase and Stevens and Bessy become unwilling allies in Cacopoulus' revenge against the people who deserted him and framed him to get their money back.