I don't think the cover painting is by Morris Gollub - it doesn't resemble the work he produced at any time. Instead it looks like the work of George Rozen (1895-1973). He produced numerous covers for Western magazines, such as 'Masked Rider' (1934-1953), 'Range Riders' (1938-1953) and 'Rio Kid' (1939-1953). He usually signed his name at the bottom of his paintings, but this one may have been photographically cropped for printing. If the original survives it might settle the matter - his work now sells for high prices on the art market.
Link to the book:
0255 - The Ranger