[FC] Intermittent engine turning itself off

[Steve Turner]

Hello gang;  I took the '61 Rampside out for a ride today since it was sunny and only a bit chilly here in southwest Michigan.  I drove the Rampside about 6 miles before a symptom that I had experienced this summer reoccurred.  The engine stumbles, the gen light comes on causing the truck to slow, then the engine kicks in, the gen light goes off and things are okay.  After 6 miles the problem reoccurred at irregular times, but in the last 3 miles home it must have occurred at least 4 more times.  Last summer I had thought that the weight of the key fob I had attached to the ignition key might be the cause of the problem, causing the ignition key to be pulled a bit away from run position.  I checked this out on the way home today and found that it did not seem to be related at all.  I have not done anything else to check for the cause.  Any leads as to probable causes?  Since it seems to happen once the engine is fully warmed up could it be
 coil?, fuel pump?  what else?
Many thanks in advance.  Steve '61 Rampside(with car engine), '61 Lakewood