Republic assigned their house-contractee Associate Producers to various series productions over the years, such as Melville Tucker was given the Monte Hale series to oversee and Gordon Kay had the Allan "Rocky" Lane films.
"Sundown in Santa Fe" was intended to star Monte Hale as part of house-employed Melville Tucker's Associate Producer films for the 1948-49 production season....but, toward the end of the first day of principal photography, Hale fractured his arm and was taken off the film, and contract player Allan Lane was his replacement.. Some second-unit work, involving stunts, had already been filmed with the stuntman wearing the clothes Monte Hale had for the film. Republic was not one to scrap film just because of the star's costume, so Lane was given Hale's usual white pull-over shirt( with no buttons) and a string-tied front and trousers to wear in the early scenes shot in the sheriff's office in order to match the long-shot footage already shot. He got back into his usual "Rocky" Lane costume ( buttoned striped shirt and Levi jeans) for most of the film. As with most series, then and now, some fans could (and do) recite every line and describe every frame and camera set-up in each entry, and the real Gung-Ho "Rocky" Lane fans were no exception. And for years have debated as to just why this was the only "Rocky" Lane film in which "Rocky" had a costume change.
Because it wasn't intended to be an entry in the "Rocky" Lane series is why. Part of the net result was that Melville Tucker became a one-time Associate Producer on one "Rocky" Lane entry only, Monte Hale starred in one-less film and Allan Lane in one-more film than originally scheduled for the 1948-49 production season.
The Republic production sheet on "Sheriff of Sundown" lists Monte Hale as a cast member. And as far as Republic was concerned, he was. Not because he was in it---he isn't---but because the bean-counters in the front office charged off the days he worked on the film against the budget of the finished film.
This one has a lot of plot; Army Intelligence is trying to track down the evil genius they think was behind the plot that led to the assassination of President Lincoln, and they think he is in the Santa Fe area, which is being plagued by robberies and murders and, at the scene of each crime, a dagger bearing the inscription "Sic Semper Tyrannis" is found. Well, shades of John Wilkes Booth. So they assign Monte Hale to the case and, after Hale fractures his arm, have to replace him with Allan "Rocky" Lane. On top of that, the Rancher's daughter (Jean Dean) is a flirt and a vamp and uses her feminine wiles on the sheriff's son (Rand Brooks) to keep her and her father (Roy Barcroft), both working for the "Sic Semper Tyrannis" villain (Trevor Bardette), of any activity by the law that might endanger any activities of their own.
Republic also thought that Minerva Urecal's role name was Ella May Watson.