What's got me confused Joe is the part about the light being unique and the bulb having it's own rubber washer. The car tail light housing is nothing like that.
Car tail light.

I see for the pics of your truck the light is different though so I won't be able to help since I have no experience with those.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.