There should be a ballast resistor between the 12 volt supply line and the coil. It is supposed to be impedance matched to the coil. Not sure what the resistance rating should be, but somebody here should know. Some cars, but not this Dodge, I think, have a resistor wire, rather than a stand-alone resistor. These usually have a specially marked wire jacket that is distinct from the other wires.
Now the 64 dollar question is why would you have the key on without the motor running? just been through this issue with a pal of mine. 54 chrysler engine dual points. Don
basic system, should look something like this: With the ignition on, it is very common for the points and coil to get hot if they stop in the contact position. If you plan on leaving your accessories on while the car is off, use the acc position on your key switch or install an key switch that does.