When Monte is breaking the Gray that Shorty never could break, a flank strap appears and disappears throughout the ride.
At about minute 3 of the movie, Chet and Monte kill a wolf for its hide. At that time, there is no other wolf on either of their horses; one minute later into the movie, they ride into town with a wolf on each of their horses. However, when they dismount, both wolves have just disappeared. They reference that they have them, but they are not seen again.
Monte sports a mustache/is clean shaven randomly throughout the movie, although he potentially could have shaved and regrown it.
Fightin' Joe Hooker, the cowboy riding fence, says he rode with Joseph Hooker when he led the Army of the Cumberland at the battle of Lookout Mountain during the Civil War. General Joseph Hooker did not lead the Army of the Cumberland. He was in command of the XI and XII Corps of the Army of the Potomac and was sent west to reinforce the Army of the Cumberland, which was under the command of General George H. Thomas at the battle of Chattanooga, of which the battle of Lookout Mountain was part.
At about the 40-41 minute mark when Shorty is leaving the crew, he is holding a green plastic or vulcanized tarp with grommets, very similar to those issued in WWII.