The only way for an engine to run backward is for a cylinder to not complete its cycle at very low speed, and 'kick' the engine in reverse. The starter is incapable of performing this - even if IT ran backward - because of a one-way clutch on the drive gear. This can barely be sustained as the valve timing (ground for clockwise rotation) would be very, very late and any 'fuel' would need to be supplied from the exhaust system.

Have you actually SEEN the pulleys rotate CCW?

For the helluvit... take off the distributor cap, rotate the engine CW until the ignition points just start to open (twisting the rotor against the spring tension should make them open further). Place your finger or a piece of tape directly below the rotor tip and position the cap back on the distributor body while observing how closely the mark aligns with one of the 4 towers. I am thinking that the dizzy was assembled incorrectly or has the wrong breaker plate, putting the rotor between terminals when firing.