When I used to run Mallory ign I took spares of everything(module,coil,roll pin etc)with me when I went on long trips.
I had a coil that acted like what you describe.
It was a promaster and it would start and run fine then after some heat it would miss and act up just like George described. At first I thought I had a roll pin problem(that came later but thats another story)because of the backfire. I changed the coil and it was fine until I took that ignition off of the car.
Good luck on your trip.
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