Why does engine cut off after idling for awhile?

On this 65 Valiant 170 I've got. It starts up easy and idles good. It's got the most vacuum I can get out of it for it's wear and tear. It's between 16-18 in-hg at idle. It appears the motor has some miles on it but it idles smooth and no unusual noises. All electronics have been gone through and many replaced throughout the last 2-3 years and not driven but a few miles. I usually start it up, get temp up, and drive it around the neighborhood a few times since it's not perfectly streetable. Now it's developed a symptom of dying minutes after idling smoothly. I start it and let it fast idle for a minute and then hit the gas and idles around 600-650 real smooth and quiet. I let it get up to normal temp, but sometimes it just cuts off. It has fresh fuel too and it has 5-6psi fuel pressure too. It's still running points which the distributor was changed out with a reman probably 2-3 years ago but probably only been driven 10-15 miles but started and idled on a regular basis. Any ideas? Ballast resistor, maybe?