I recently purchased an 87 245. I've run into some trouble with the tail lights, and i'm rather confused.

I'm going under the assumption that the top lights (the red lenses) work as brake lights (normally):
the bottom brake/tail lights work, the turn signals work and the reverse lights work, however, the top lights do not. I tested the wires and they get nothin'. Furthermore, the back windshield brake light doesn't work. I'm also assuming the back windshield brake light is part of the tailgate harness.
My main question being: can i just splice into the functioning bottom brake lights in order to get the top lights and back windshield light to work? Is there some other function these top lights have that i'm overlooking?

Anyways, I'm new to this forum and would appreciate any guidance.

Thanks in advance,
Christopher

fog lights