They aren't clutch heads. The heads are oval extrusions. I have no idea why they made a special (expensive) screw on these. I use pliers. I have yet to encounter one that wouldn't come right out. They don't seem to be marred by the pliers either.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission