Use permatex high temp RTV sealant, get it in black otherwise any other color will show through, you can use clear but black is preferrable, check your local auto parts store for it like I know Padik auto parts in Califon has it. also get painters tape to cover the lenses so you dont get any drippage because it can get sloppy and its not easy to clean up.

hey, whats the name of the sealant that you used on the headlights?