Only 69/70 GT500's need the recall it seems and indicated by Ford. The correct non vented caps used back in the day are very hard to find. Of course the non vented gas cap is best . If you do the recall venting described in the recall illustration provided in the link then even if you do only have the vented gas cap that came from the factory the chances of excessive fume build up at the vented cap will most likely be negligible. The pressure/gas fumes is going to take the path of least resistance which in this case is the more open pathway of the venting tube compared to the small venting port on the vented gas cap.