well kinda off of what edgeaholic was talking about.....driving lights are best mounted higher up. they are designed to project the light a far distance ahead in a sharp pattern. mounting them lower on the truck (valence for example) will prohibit them from reaching their distance potential. on top of that, it is not legal to drive with "driving lights" on. now, i've never in my years heard of a legal way to wire them and an illegal way to wire them, but they cannot be turned on while on the road. as it is, they really won't do as much good for you on the road as "fog lights" would. fog lights have a shorter throw, but a wider dispersment of light helping you to see better all around you as opposed to a mile down the road.
i personally do not wire aftermarket auxillary lights with my high or low beams. i wire them independently from the headlights all together. the benefit of having them, is the ability to turn them on whenever you want/need.
i digress. back on topic, if you're mounting lights down low in a valence and want to use them during daily night driving, you want fog lights.
if you want driving lights, mount them on top of the bumper at least, or behind the grille. another common place for DLs is on a roof mounted light bar or roll bar.
1995 Ford Ranger XLT | 4cyl | 5spd | ext. cab | 2wd | Tuff Spray-in Bedliner | Pioneer DEH-6500 h/u | Kicker KS525 5.25" in doors and rear panels | PPI 4480 4 channel speaker amp | Profile BA400 sub amp | JL Audio 10w0