They don't know what the hell they're talking about. Those are not Hemi heads. They are though very rare, indeed. I actually never knew that a running example existed. Learn something new everyday.
What they are, is canted valve heads made for the small block Chevy, very similar to big Chevy heads. They only made a few pairs and as I said, I never knew a running example was out there.......but there it is.
That's pretty dang cool.