Death Kiss(1974)

Jim Preston receives a yacht as an anniversary present from his wealthy wife Ellen. He plans to kill her for her entire fortune. To carry out the murder plan, he makes a contact with Mike, a crazed rape killer who has been terrorizing the city. Mike agrees to be the assassin for a large quantity of heroin. However he suspects that Preston will kill him as soon as his assignment is complete, so he finds a woman who looks exactly like Ellen and kills her instead.