I just installed Hella FF75 fogs and Hella 500 drivings last weekend. For the FF75's there are already holes in the bumper, so you just bolt them right on! Easy as hell. For the 500's I just made use of the 2 holes at the bottom of each stock foglight location and made an aluminum plate with 3 holes each... 2 for mounting the plate to the holes, and 1 for the bolt from the 500's.
Lighting output difference is literally like night and day.