Intermittent issues such as you describe are virtually always ignition related.

If it was "fuel related", and it ALWAYS seemed to "run out of gas" after about 5 minutes, after checking the fuel filter (you did), and the tank vent (don't know if you did), I would have checked the fuel pump (apparently you did not test, just replaced). And then I would have found the ignition issue.

I am totally with Jerry on the pertronix.

I won't attempt to convince you that points are much more reliable (they are!), just suggest that if you are in love with the electronic gizmo, carry a complete spare in the glove box (also carry a complete spare distributor set up with points and condenser, just is case the spare also fails!).

Jon

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
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The Carburetor Shop