Interesting. This past week, I had to make two trips to LV to pick up - drop off my daughter at the airport. I stopped counting the number of pickups pulling 5ers that their headlights were lighting up the top of telephone poles.
If the rear of your truck is sagging 3", you better bet that your headlights are way up there and blinding everyone coming towards you.
Air Bags or other devices to get your headlights back down to normal setting is a must!
Ron