51) He had the head of a dead man. (about the ghost's appearance)
Most people, dead or alive, have only one head each. You can have 'a dead man's head' but not 'a head of a dead man'.
2) She had the voice of an angel. (describing a singer's voice)
Angels, if you believe in them, have only one voice each. He could have 'a voice like an angel's (voice)', but not 'a voice of an angel'.