I don't think you can. The valence with fog lights come on 4x4 trucks unless its an edge (not sure if xlts had them) but here are two pictures why I don't think it will work
with or without flares, you have that part of the valence that attaches to the top corner (the part that meets up with the flare in the first pic), something that your 2wd bumper doesn't have a spot for to clip in. the 4x4 bumpers have an indent with slits cut into it for the top corners of the valence to clip into.
If you have a certifit near you, go there for a bumper theyre really cheap.
2004 Vermillion Red 4.0 4x4
3" Body Lift
2" Tuff Country AAL
33x12.5R15 BF Goodrich Mud Terrain KM2 on 15x10 Mickey Thompson Sidebiter II
& lots more