318 Poly idling question

65 Power Wagon, unknown year of 318 Poly, but guessing around 65. New fuel pump, manual choke, still has points. Ran great with no problems up until a few days ago. Close the choke a bit, fire it up, idles good and strong for about 5 minutes, then stalls. Try to start it again, the starter cranks, but won't start. Then if I leave it alone for a while, go out to it again, same thing. It will start and run for 5 minutes, stall, etc etc.
Any ideas?