John Holmes did one film that was shot with angles to suggest he was fucking a man but most of the time he was pumping some porno starlet. There were, apparaently, two scenes in which he did truly bang another man up the ass. One of these men was HIV positive (unknown to anyone at the time) and Holmes later contracted the disease, theory being fromt his movie. The film was shot when he was down on his luck and broke. he wasn't into men but did it for the money.
Peter North is another story. He likes guys. He goes by Matt Ramsey when he does Gay porno, I think.
This knowledge brought to you by useless porn research a few years ago.