1965 Dodge Dart Door Locks...

Not everyone is the "do it yorselfer" when it comes to those tiny springs and such.
If your willing to try, there is a guy parting some early Chrysler products (furys and newports). So rather than deal with worn out door/ignition keys and locks, grab a trunk lock and key. Build you door and ignition lock cylinders to that key which has much less wear. Any locksmith should be able to help.

Yes, by all means replace your cylinders.Once they are worn they will be trouble from then on.A locksmith should be able to decode your key and cut a new back to factory specs and key the new cylinders accordingly.New cylinders are so cheap it's not worth getting used ones. I buy the cylinders for about $16.00.