99 and 2000 didn't have them, and don't have the wiring for them. I had a 2000 back when they were new, no signal mirrors and the mirrors were black on a white truck.
now, i understand they are a direct swap...does the 99-00 Lighntings have the wiring for the these mirrors with blinkers to plug in to so that they will operate when the blinkers are engaged?
I posted a thread to see if 99-00s had the wiring. First person says theirs has it in their 2000. My 2000 also has it. Another person also replied that theirs did. Safe to say the wiring is there??