The Stovebolt Site Forums The Shop Area The Electrical Bay engine runs, then quit while idling, now will only run with starter engaged

How about checking if you have power to the ing. points. with the distrubitor cap off and the key switch on check if you have power to the coil and at the contact breaker points. If so start it until it quits. Then check again before you turn the key switch off.
As said before You have a loss of power in the system. maybe even the key switch itself.