Most 1999-2003 SD 's should have empty bulb sockets under the red reflectors in front doors.
Pry off reflector on side closest to motor. Insert 194 bulbs, I think
Clears lens are now obsolete,... part no for clear lens was 1C3Z-13731-AA. The part number is for half clear lens, not full red as in picture.
Full red part number is F81Z-2523820-AA
You could drill out or dremel out area of your red lens near the bulb, and graft in some very thick clear plastic material

 

Its a little more than adding a bulb. It also changed by trim level through the model years. My 2001 XLT had them, my 2003 Lariet did not. Here's a conversion from a pictorial I did 15 years ago to a video. It still needs editing and some photo work.

 

TooManyToys, that was quite a nice presentation. I really liked the aluminum duct tape for more reflection. I will add that.
But my suggestion is for the guys/gals who did not know that in many of the early SuperDuties bulb sockets are already in place.
Once again though, thank you for the skilled tutorial!