Please HELP!
I recently inherited an oil painting painted by John Leone.
I know that the art was on the cover of one of Louis L’Amour’s books. It is of 3 cowboys and a pack horse in front of tall desert peaks in the moonlight. The first and the third cowboys are pointing pistols in the air and middle cowboy has a rifle across his lap.

Does anyone know the name of the book that this painting is on?

Thank you!