I recently did the foglight mod on my '98, which is kinda why I'm curious as to how it gets done on the earlier models. The fog lamp circuit is a little different than on the '97.
With my limited knowledge and experience, the hard part of the mod for me was figuring out where to get the alternative power source to feed the fog lamp circuit. After studying a lot of '98 wiring diagrams, I finally discovered that the park lamp circuit also feeds a relay in the trailer hitch circuit, and so I was able to tap into the the wire that powers the trailer hitch relay to make it also power the fog lamp relay. Works great. Maybe you can do something similar on the earlier models?
Good luck with the mod in any case.