This movie was a homage to the old spaghetti western. The first music is the music from Django (1966) and the last one was from They Call me Trinity (1970)
Django credits (1966)
http://www.youtube.com/watch?v=MQKKOjXIwuA
They Call Me Trinity (song)
http://www.metacafe.com/watch/7013082/terence_hill_bud_spencer_they_call_me_trinity/
Also there are many other references to the western movies like The Good the Bad and the Ugly for example.