Hillbillys in a Haunted House

The name of this movie is Hillbillys in a Haunted House released in 1967-05-01 and it's main theme is Country singers on their way to Nashville have car trouble, forcing them to stop at an old haunted mansion. Soon they realize that the house is not only haunted, but is also the headquarters of a ring of international spies after a top secret formula for rocket fuel..