When we went to Spain a couple of years ago, we were in a store that sold candy and I was immediately drawn to these. I have a package that came with a keychain of their "mascot". http://www.darkformula.net/files/Smilies/emot-haw.gif
At interstate speed, turn the wheel back and forth. If it goes away when you turn the wheel and unload the bearing, that's the problem. Bearings on Mustangs are internal to the hubs, so you would need a new hub.
No, the mechanical interlock that prevents the car from being pulled out of park. Of course it's a band aid, and you could pull the car out of park at any time, but it worked for most cars until the 90's.
Remove the actuating lever that won't let you take it out of park, but leave the electrical actuator so the car doesn't know what's going on. Let me know if you want help.