Sometime, but not always, the starter will not do a thing when the key is turned. No other electrical system is affected, lights radio, original ac all work just fine. I checked the ignition switch and it shows no resistance in any position and the starter will engage when you short the poles.
What a great old car! And only 52K! As far as the problem, do this. Have a helper turn the key to the start position while you check for voltage to the smaller wire on the starter (solenoid). You should get 12 volts. If you don't, check the starter relay. The old Chrysler starters used to have problems with the solenoid. There is a copper connector inside them that would wear out over time. When you turn the key, you might get a click and nothing else. Keep trying, and they would start. That is the most common problem they had, but it sounds like yours is a little different if it starts when you jump the solenoid. Check to see if there is power there. If there is and it doesn't start, then the solenoid is my first guess. Today, it is much easier to get a new starter that will come with a new solenoid, so that would be your choice.