Following this thread - Woody - when you said you changed the coil, cap and rotor and the next morning the car wouldn't start - cranked but no fire - then on second try it started instantly - then it exhibited the same problem while driving. What about this scenario - an ignition switch on the way out? When your car acts up while driving - does it happen after hitting a bump? Next time it acts up - try hitting the switch and the column and see if it makes a difference. If the switch is going defective - loss of 12 volts to the ignition system can cause the symptoms - maybe through the ignition switch. Gremlins can be a pain to troubleshoot but easy to fix when found. The more I think about your symptoms the more I think the switch could be a possibility. Worth a shot.
Morris