Pickup truck squatting when loaded - headlight aim

If the truck sags at the rear then it needs more leaf springs or new leaf springs to carry the load. My truck as a double leaf set of Supersprings and it is level when the bed is empty and level when I have a 3700 lb. load on the rear of the truck.

It is not just that the headlights are pointing too high and blinding oncoming drivers, but that the weight distribution will be off and not enough weight will be on the front wheels and that affects road handling and braking.