Check the grounding of the LR light socket. It's possible for the tail light circuit to find a ground by backing up through the brake light wire until brake or turn signal voltage is applied to that wire- - - -then everything goes dark. It's not uncommon for the socket to lose its ground due to a loose or rusty attachment to the bed.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!