As soon as it dies and does not re-start, immediately go and pull the distributor cap.With the key in the on position check to see if it has fire at the points.
One more thing,like chiphead said, it could possibly be is the fuel line is getting hot and evaporating the fuel befoe it gets to the carb. Try the clothes-pin trick on the fuel line.Put about 6 or 7 of them spaced apart .they will act as a heat-sink and prevent the fuel from getting too hot.
