There is a plastic liner inside the tail light housing, it protects the paint and helps keep dirt out of the housing....they are pretty tough to find and are usually rotted away. I think they are also attached by some pins and do not come off without drilling the heads out. I think I have a picture somewhere of some I have, let me look
Yea, I haven't had any luck so far, mine are pretty well done for, I ordered some lights online, hopefully those come with ones in a better state than mine
But thanks anyways guys!