Here's one other thought. Once upon a time I had a '64 Nova that was my daily driver, and one day I was driving home after work and it just stopped running. I coasted to a stop on the side of the road and did all the normal tests you do (is it getting air, fuel, and spark?), and everything seemed to be working, but the engine wouldn't even try to fire. So I pulled the distributor cap to check the points. The points were fine, but with the crank at tdc on #1 cylinder, the distributor rotor was pointing at the #4 spark plug wire instead of the #1 wire. Not good. So I pulled the distributor, and lo and behold, the roll pin holding the distributor drive gear in place was mostly gone. There were a few scraps of it left, so friction was the main thing holding the gear in place, and it had slipped about 120 degrees, which caused the engine to stop running. You might want to take a look at the drive gear on your dizzy and make sure it's in good shape along with the roll pin holding it in place on the shaft.
