Both tail light do not work but the brake light and back up do

you are missing a ground wire
what is happening is when you have the tail light on it is grounding out through the brake light so that when the brake is applied the current is stopping that taillight working by pushing current back through the bulb
the same principle that puts out the charge light when the alternator starts working

brakes and turn signal lights work together not tail and turn your mistaken

Brake light switch under dash and actuated by the brake pedal lever is out of adjustment or faulty. Adjust or replace it and you'll have your brake lights back. The dim tail lights may just be that you have possible replaced them with the wrong bulbs or the ground to light housing is faulty.

You probably pinched a wire when you put the bed back on. You most likely have a blown fuse as further proof that you shorted out everything in the back of the truck.
Recheck all your wiring paths.

could be a glitch in the front power controll modual disconect the battery wait couple minuts reconect and see if thay come back
also replace the bulbs even the one on the cab your therd brake light alot of ppl dont relise its out and it will help determin if its in the tail lights or its in the brake switch if the therd brake light lights and the tails dont replcae the switch after inspecting the tail light conectores for corotion

if rear window stop light works has blown globes in other 2 tail and stop are different circuts fit 2 new globes only go in 1 way

That does not make any sense. Do the tail lights work? There are supposed to be separate filaments for brake lights, tail lights, and turn signals. In particular the center brake light should not be possible to be confused with tail lights or signals. Does it come on? If not, then you probably have no brake lights at all, and that is probably because of the bad fuse or the switch on the brake pedal for the brake lights.
If there is some sort of cross over between tail light and brake lights, that is usually from a bad light socket ground; which results in current backing up from one system to another. But then each is usually only half brightness.

It goes straight from the switch to the tail light circuit
make sure you don't have a bad tail light socket


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If both tail lights are not working it is likely to be a fuse or bad connection under the hood or a connector at the back see if you can trace the wires to a connector and see if it is dirlty or corroded.

check fuses