It's very likely fuel related. Yours, like my Valiant is 56 years old. Unless you've removed and cleaned and or replaced the tank, it's probably got lots of rust and debris in it. That's the source. You can verify this by removing the fuel filter. Get a clean WHITE paper towel. Tap the fuel filter INLET in the towel. If you see all sorts of dark debris, there's your answer. Since it is a point type ignition, you could also be experiencing a points failure. You can tell that by attaching a dwell meter and taking a dwell reading. Could just need a tuneup. The good news is, that unlike a modern vehicle with lots of sensors, your car only has a few different systems. They are easy to diagnose.
Go here and download the 1966 Dodge Dart service manual. That's the closest one they have and will be "close enough" for what you need. It will have all of the correct tune up specs and such and tell you how to do whatever may be ailing your car.
