Steve: I think you're overstating what the Muchmore film shows vis-a-vis the Zapruder film.
But that doesn't mean that some of what it shows - critical parts of it - supports what we see in the Zapruder film.
The main claim by the alterationists is that the Z film was altered to hide the blowout in the back of JFK's head. And that BOH blowout indicates that JFK was shot from the front.
But the Muchmore film, to me, shows no such rear blowout. As to the angles of Kellerman's head, et cetera. That for me is of secondary interest. Why would it be necessary for the alterationhists to touch those areas? The key, again, is the BOH.