That has always been the positive aspect of Tarantino, in my opinion: His love for the pioneers of the SW-music!
The tracks "Dopo La Condonna" (you know, the SW-version of "Für Elise") and "La Resa" from "La resa dei conti" are perfectly used. And as you said, the themes from "Il ritorno di Ringo", "Un dollaro bucato" et cetera, are also used.
The most interesting choice of music isn't a SW track though... No, it's "Un Amico" from Sollima's 1973-crimeflick, "Revolver".
@ 2:42: http://www.youtube.com/watch?v=PU7Vam1KCPU