Deaver

Deaver has been building leaf springs for trucks and off-road vehicles for decades, known for packs that keep a rear end level and controlled instead of sagging under real-world loads. The fix for rear sag usually isn't just bolting in a "heavier duty" pack: it's matching spring rate to your actual payload and ride height goals, since an overly stiff pack rides harsh empty while an overly soft one still sags loaded.

Towing capacity, camper weight, and how often the truck runs empty versus loaded all factor into which pack actually solves the problem instead of just changing which extreme it fails at. It's a name that comes up in nearly every serious leaf spring search, alongside Eibach, as one of the two most trusted options in the category.