OK, I just looked through the manual from the glove box. I couldn't find any mention of which lights light up when. Next plan is to take it to the local Ford dealership and see if they can help in any way.

 

Well, the ford dealership is telling me they should light out but they are out of the correct bulbs.

 

Do what many of us here have done, buy Sequential taillights and problem solved. I bought mine from Webelectric. Comes with a lifetime warranty. Very easy installation....like 15 minutes tops!

 

I literally am paddling the same boat you were. God I feel dumb now

 

You could show them the rear lamp electrical diagram from the ford service manual, but I doubt they are smart enough to understand.
http://iihs.net/fsm/?d=40&f=Parking,...0Lamps.pdf&p=1
clearly shows that only tail lamp left and tail lamp right have only 1 wire that turns on when the lights turn on, the "park/stop/turn" lamps 1 & 2 on Left and right rear get 2 control wires to the 2 filaments one for lights on, the other for turn/stop/hazard.

 

The two outer lights, light up for brakes if you has stock lights. If you go to sequential lights like I and many others have done then all 3 will light up.