[James]

Did you check the centrifugal advance in the distributor? If the springs had broken it would go full advance while running. Turning the rotor by hand the distributor should rotate clockwise against the springs. There should always be some spring pressure on the rotor and no looseness (no spring pressure/feel sloppy). Another possibility if you had just operated the engine to over 3500 rpm, it is possible that the centrifugal advance had stuck in the full advance position from dried up lubrication.

You can see if the engine will run by resetting the distributor to fire on the crankshaft timing mark. If it run OK, then you rule out other issues. You will need to repair or replace the distributor.