You could get away with mounting them on the OEM lowers by bolting through the open mesh but they would be positioned alot closer to the center line that way. Mine has one end bolted through and one self tapper going into the solid portion. I doubt you'll ever see the hole once they're removed unless you get right down there and look for it.

You could also fab some sort of "L" clip that you slip behind the upper edge of the lower grill. They should stay in place once you snap the grill back in place.
Some of the DRLs are even light enough to possibly be velcroed in place.