As I understand it, Ford did not offer factory fog lights on a Super Duty (of any trim level) until mid year 2001.
ALL of the headlight switches "pull out" and on the earlier trucks it is part of the removal system to pull the switch panel out from the dash. Just because your switch pulls out does NOT mean you have a switch that would support wiring up the fog lights to be triggered from it.
It seems that there's no real good option for a clean factory type install of fog lights on a truck which didn't come with them from the factory.
I recently did an '05 front end conversion on my 2000 model and the front end parts I bought came with the factory fogs. The best way I've come up with to wire them up is to get some 9005 pigtails from the parts store to plug into the factory fog lights, then wire them up to be powered directly from the battery, and triggered via relay off the parking light circuit. Personally, I don't like the idea of the fog lights ALWAYS being on with the parking lights, so I'm also going to put a switch in the circuit so that if I want to run the parking lights without the fog lights I can. That way also, if I do have the fog lights switched on, as soon as I kill the parking lights, whether the fog light switch is on or off it will kill the fog lights as well so I don't have to worry about accidentally leaving them on and killing the battery.
Between triggering them directly off the parking lights vs directly off a switch, at least for me, I think combining the two approaches is the best.