Sergio Leone film this is the extended version with 178 min, while the regular dvd previoulsy released by MGM was 161 min.
Excerp from DVD Savant:
With an additional eighteen minutes of new scenes GBU is still the same picture with a redistribution of emphasis. The new material fleshes out the characters of both Eli Wallach's Tuco and Lee Van Cleef's Angel Eyes. There's more melancholy about the slaughter and waste of the Civil War. The longer version patches some gaping continuity gaps as well. This cut brings GBU almost back to its full premiere length in Rome in late 1966. It is longer than any cut released in theaters to paying audiences.
Film-wise, much of GBU was rebuilt from the ground up. With a copy of the full Italian version and a Techniscope negative, MGM archivist John Kirk engaged the film restoration company Triage for the film work. They rematched most of GBU by eye and reprinted a new 35mm 'scope conversion negative. That process is covered in one of the documentaries on the disc but what isn't made clear there is that the negative supplied from Italy had flaws. For some sections of the film it was decided to fall back on a good 35mm American dupe negative instead. You can see some of the problems in the restored scenes: mottling in the sky when Lee Van Cleef arrives at the ruined Rebel fort; yellow staining in the new scene where Tuco and Blondie ride a wagon through a battlefield.
The one completely new scene is called The Grotto. In it Tuco recruits three bandits to murder Blondie. This is the only scene not shown in the original Rome engagement in 1966, before GBU was cut to 161 minutes for general release. John Kirk elected to retain The Grotto because producer Grimaldi categorically told him that it was part of the official cut of the film at the Rome Premiere and was dropped from the first release only for time, against the director's wishes. Kirk reinstated it with the producer's blessing. The restored scene fills GBU's most glaring continuity gap. Without the action in the Grotto, the three gunmen who try to ambush Blondie are unmotivated and gratuitous. The scene also presents Tuco as an accomplished manipulator instead of a malcontented loner.