I'm sure this has been mentioned already - just can't find it - but this doc on Gian Maria is really well done. It's on the second disc of the "Bullet for the General" blu-ray. I really learned a lot about him that I didn't know - such as he was considered one of the great Italian actors of his day (most Americans have never heard of him), and the film industry all but abandoned him at the end of his life.
There's only a brief mention of "Fistful of Dollars", and no mention at all of "Few Dollars More" (odd as it was the highest grossing film in Italy for years).
Also nothing about"Face to Face". That was disappointing (although I've read Volonte' hated the Leone films), but it's a great watch overall.