Removing a radio from a 50K is alot easier than the 51-5 cars. There's a bolt on the top/center of the firewall that needs removed...it holds a bracket under the dash that's attached to the rear of the radio. Then, just remove the knobs from the front of the unit and unscrew the nuts that hold the tuner/volume shafts in place. On some...including this model, to remove the nuts, you may need either inside snap ring pliers or a pair of needle nose pliers with a narrow head as the shafts are held in place with the same style 'nut' that holds the switches in place. Once the rear bolt and front retainers/nuts are removed, you can drop the radio out from under the dash. Oh..and don't forget to pull the antenna wire and to unhook the power line!
By the way...who's parts car is it? I might be interested in a widget or two from the car.
Jimkf