I'm intrigued by the front airsprings
They are an ez install and are available on Amazon Prime for the best price anywhere.
I currently have SUMO Springs on the front, but these Air Springs may add additional lift and softer absorption from bumps on bad roads.
Amazon-Air Lift 80531 for E450 Front
In my opinion, the Vegas/Axis rear leaf springs are plenty sturdy. I currently have SUMO Springs on my rear end so I'm not interested in Air Lifts for the rear.