To the OP.
That dist is likely siezed to the block as a result of galvanic corrosion between dissimilar metals.
IF you happen to break it off trying to get it out, consider upgrading to a DuraSpark electronic distributor. It's a drop-in as far as the dizzy itself, but you will have to install a module and do some wiring mods as well.
Search here at HR for a diagram.
If you do decide to go this route, use a dist cap, cap adapter, rotor, and wires from the 1977+ application ... which spaces the plug wires further apart and prevents arcing and misfires.
Ford also released a "campaign" distributor in about 1981/82 which was re-curved in order to cure a detonation / hot start problem. I can't recall the dist tag # (E2TE-12127-AA ???) but the vac advance had a "WIN" label on it.