Only the specific schematic diagrams will tell.
Follow this link and enter in your vehicle. They will give a list of radios that will fit for you to compare. They also list what adapter kits and tools you will need for install. Best of all, they even give a detailed set of instructions on how to remove any access panels and complete wiring details.
[ Crutchfield.com Link ]...
AS you clearly have no clue what you're doing leave it to someone that does.
Check out the12volt.com. You have to join (no charge) to see all the wiring information they have but it is your first best bet.
The 1946 Plymouth? Mine didn't have a radio.
The 1992 Dodge D250? Last time I had it apart was 18 years ago. I think it was the black wires.
I won't even mention the boat horn I put on on my bicycle.