1972 Spider. Car was running great earlier this summer. Then suddenly it started running rough, like it was fuel starved with the engine hesitating and surging, then it just stops. I've had two professional mechanics look at it and neither could figure it out. Has spark, new plugs, ignition system is new, carb was rebuilt a couple years ago, fuel pump has plenty of pressure. At one point I got it started and just held the throttle flat on the floor (no pumping) and the car ran for about 60 seconds surging, coughing, then stalling. Then call AAA. I'm at a loss. Ideas?