Premise: Guns of Diablo is a Metrocolor 1965 Western directed by Boris Sagal, starring Charles Bronson, Susan Oliver and Kurt Russell. Charles Bronson is a wagon scout (Linc Murdock), who runs into difficulties when he meets old flame Maria (Susan Oliver), now married to corrupt lawman Rance Macklin (Jan Merlin).
Hypothesis: Guns of Diablo was popular in 1965.