The Train Robbers (1973)

The lure of gold brings a number of people to the railroad watering-stop of Liberty, Texas. First to arrive is a trio of aging Union army veterans: Lane (John Wayne), Jesse (Ben Johnson) and Grady (Rod Taylor.) Together, with drifters Ben (Bobby Vinton), Sal (Jerry Gatlin) and Calhoun (Christopher George), they plan to accompany Mrs. Lowe (Ann-Marget), a train robber's widow, to the site where her husband had hidden a gold shipment. Lane observes that his band of adventurers will be hotly pursued by the deceased robber's gang members along with "every two-bit gunman in the territory." As the company crosses the Texas border and Rio Grande River in Mexico, just ahead of of a band of pursuers, a lone, well-dressed, cigar-smoking stranger keeps a careful eye on both groups.

IMDb: https://www.imdb.com/title/tt0070825