it may not be that necessary to ''add'' a wire for gnd. as LONG as you have a really good scrapped surface where the fog lamp attaches @ the bolt hole.
WTBS w/ that being said
most want a good paint job and usually where the lamp attaches to the truck it's painted.
so
open the lamp usually by removing the lens ring.
push a green wire up thru the mounting hole. ground is green.
attach it to any part of the housing or lug
or
where you see the second wire from the bulb that is attached to that lug, wire there.
now you have a separate grounding wire. if you make it long enough to reach the second fog or at least bring them both together to a common bolt that IS a good scraped area ground. i like to use a serrarted washer.
the other two wires from the fog lamp then go to the ''switched'' side of the relay. if you can try & place the relay[s] close to the front of the engine compartment.
BTW
relays [bosch 30 amp] can be found at any automotive electrical supply or FLAPS.... about $5-6 bucks w/ the relay, solderless connectors and plug/holder.
http://s67.photobucket.com/albums/h298/1951otter/?action=view¤t=2650080-R2-026-11A.jpghttp://s67.photobucket.com/albums/h298/1951otter/?action=view¤t=0732700-R1-034-15A.jpgask again if you get lost
