If it won't CRANK - it's a starter issue. From your original description people could not tell if it would not crank, or if you had a no spark condition. It sounds like you have an intermittent no spark condition. With the key in the START position you bypass the ballast resistor and crank the starter - full 12 volts to the coil. When you release the key it returns to the RUN position and the juice to the coil is reduced by the ballast down to 9 volts. I would put the key in the RUN position )don't crank the motor) and check the voltage with a voltmeter first at the coil and then back at the ballast. The re-check the voltage while jiggling the wires going to the coil and then to the ballast - see if the voltage goes to zero - if so, loose connection somewhere or a break in the wire. Check the ground too on the ECU - the factory used a self tapping bolt with a star washer like the ones on the starter relay to cut into the steel body of the ECU. If all that is good check the gap at the reluctor in the distributor - .006 - .008. The DC distributor, if it's the older style, is really a factory distributor and will have the set screw and adjustment slot. If all that fails replace the pickup in the distributor - the thing you set the gap on.