George Foreman vs Sonny Liston in their prime, who wins?

Who would have won if George Foreman would have fought Sonny Liston if they were both in their prime? I have to confess this is a hard one to pick but I would sway towards an undefeated Foreman to win by a knockout within 8 rounds. But Sonny would have had an excellent chance with his power, reach, decent speed for a big man and great boxing ability and all that. But a motivated peak Foreman had all of those attributes as well pre Zaire.