I cant seem to see which "relay" you are pulling. There are no relays in the circuit for the headlamp switch. I dont mean to sound like I am trying to belittle you but are you sure it is a relay and not a cartridge fuse? Does this truck have daytime running lamps? Perhaps this is the issue I am having, that system is totally different in its wiring. Please forward this info and I am sure we can pinpoint your issue. Also is ther a factory security system in the truck.
Sorry for all the questions but electrical needs to be precise in diagnosis. I dont want to give you the wrong repair procedure.