i cant remove my distributor from my 65 390

[nik]

i am trying to replace the head gasket on my '65 and for some reason i cannot get to to come out.
i put it at top dead centre, removed the cap and rotor, and the vacuum advance then took out the bolt and the holddown clamp, at that point i expected to be able to pull or rotate the distributor, but i can't do either of those things.

anyone have any advice?