I don't know about the '66 but in the older ones, shot diaphram springs in the pressure plate assembly will result in the "my clutch won't disengage" syndrome.. so will a big mouse nest.
I'd try the "put it in gear, hold the brake, and crank the starter" method.. but i'd disconnect the coil wire first to keep it from starting, and only lay on the starter for 5 second bursts, to keep from burning up the starter motor.
