1977 Ford F-100 77 F100 Custom runs rough after sitting 14

The first suspect would be the gas has water in it after sitting that long. The other problem could be a vacuum leak. Test likel this. Get a can of spray Carb cleaner, start the car and spray around, pay attention to vacuum lines and manifold, if the idle changes, you found a leak. You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs! You might also want to clean that carb while your in there. Tap on the side of the carb with a small hammer or wrench, not hard you just want to dislodge any dirt in it.