Mike Radcliffe!
I'm sure you won't believe me when I say I was pretty sure it was Mr Radcliffe (who you may remember from such films as: Missing Link, Escape to Echo Beach, Walk on the Wild Side, My Best Friend's Lover, Bathhouse Bears , and of course, probably his best role, starring as The Slutty Professor ) but I got an email last night/this morning from a buddy in Wisconsin who says:"It's from "The Coach," which was headlined by Chris Steele and Caesar. The cap you have is from a great scene with Zachary Scott (giant cock) and a guy named Mike Radcliffe as the coach. I know something about porn that you don't? That's just craziness!"
And I could probably count on another buddy in Kansas to also confirm that the pic is indeed Mr Mike getting ready for some bigcock (why am I humming Nice Work If You Can Get It....?)