In the US version only Clint is billed above the title. In the Italy print, all three are billed before the title in the order of the title; "Il buono, il brutto, il cattivo", which translates into "The Good, The Ugly, The Bad". Not quite as catchy is it?
Next time you watch the US version and hear the gunshots over Eli and Clint's face before the title, that's where their names should go!
Example of the credit order. Italy on left. US on the right
This may also explain why LVC's credit is only on screen for about a second in the US version. In the Italian version that space is taken by Aldo Giuffre (both men got short changed timing wise in the US version)
Eli Wallach is credited last in the US version in the coveted "and Eli Wallach in the role of Tuco" at the end of acting credits.
I suspect the US credit placements are based on arangements the actors and their management placed for billing, with Clint above the title, and Eli with special billing. LVC got the short end of the stick!