Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you. Also keep in mind I don't know if you are a pro or a novice, so feel free to add any additional info at any time.
With a problem like this sometimes the fault can be pretty elusive. Odds are the fuel pressure, or the spark are going away to cause the problem. I am thinking the ignition might be flaking out, the coil and ign box don’t have to be hot for them to have a problem, although them being cool is a plus. There is an easy out if the ignition is acting up. There is an HEI ignition system with everything including the coil built into the distributor. You just run one hot wire to the distributor, power it up, and the ignition is on, and turn the power off and the ignition is off, it is a great setup.
Beyond that if you look at the fuel system, which could be loosing it's ability to deliver enough fuel, and causing the problem, should be looked at. It is possible the pump is delivering enough fuel, but the carb float could be sticking, and limiting the fuel available to the engine. I really suspect a limited fuel volume problem, might be at the root of this problem. Fuel systems can vapor lock, or you can have a crack in a suction line where it starts sucking air, and cant deliver enough fuel under certain situations. I would start off by installing a fuel pressure test gauge, and watch the fuel pressure as the engine acts up. This will allow you to confirm whether the fuel delivery to the carb is your problem. Go over all of this and if you have any more questions at all, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer.
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