1972 duster 340 fires up then dies and will not stay running

Steven190 said
May not be related but is the 12 volt from the ignition stay hot? There is two sources of 12 volts. one from the start, when key is turned to that position. The other is the run which is the constant 12 volts.
I had a problem that it would fire but then die it was the 12 volts from the run circuit not staying on. Just my problem that I am passing on.

I had that problem too in the past. Coil had power when cranking, but not in run position, so car would start while you were cranking the starter, but as soon as you let go of the key it would die.