Clear or Amber lens?

[WHN378]

How do you know which is the correct lens for a certain year car? I just bought a 1983 and a 1986 Regal . I recently parted out a 1985 and saved a good front bumper. I am curious because the parking/signal light lens are different. One is clear with amber bulb and the other has an amber lens?

 

[Bweavy]

81-3 clear, 84-7 amber lenses