Just wanted to introduce myself and show you all the third brake light I installed recently on my '82 C10. My truck didn't have a cargo light, but I found one at the local pick-n-pull. I drilled a hole in the top of the cab, fed wired through and down the inside corner and then over to the brake light switch.
I used some automotive spray paint to lightly paint the cargo light lens red and sealed the whole thing to the truck with some black RTV.
It works really well and I like the way it looks!
More info about the truck in my
Welcome post.