01-05 and 06+ bumpers and valences dont interchange with eachother. COMPLETELY DIFFERENT designs. You'll need to get a 06+ bumper, then put the '08 round fog valence on it. 06+'s utilize bumper covers, so you'll need the bumpercover, the actual metal bumper behind it, bumper brackets, and of course the valence.
Though, the 06+ bumper will bolt directly to the frame horns on all 98+ trucks.