Just replaced my Mallory with a used '57 TBird distributor. Seller said it was just rebuilt, it's straight, no excess play, clean. It reportedly has new condenser, rotor and points, which is all consistent with what I'm seeing. I set the point gap, and the dwell while cranking the engine is at 27. With #1 cylinder at TDC (compression stroke), the rotor is pointing directly at #1 sparkplug on the cap.
The engine backfires violently and won't start.
Car was running before the dizzy changeover. I have checked and rechecked all the plug wires for correct sequence and good connections. Nothing else (coil, carb, etc.) was changed. WTH? What should I check next?