Guy in the middle in Bruce Sedley from THE OUTLAWS IS COMING. Full disclosure, if you zoom in on the name tag you can kind of make it out. His character name “Cole Younger” is on the tag and the cast list confirms the character, so I’m confident there.
So I’m thinking with the clues, it’s an OUTLAWS IS COMING reunion. Guy on left is Hal Fryar - Johnny Ringo, and guy on right is a Johnny “Billy the Kid” Ginger, the living one.