Re: Deavers Vs. Benz springs
I haven't looked into them for my van yet, but they have made us springs for out F650s in the fleet.
For increasing roll stiffness, I would to sway bars. I added a Hellwig Class C motorhome bar, and the '09 front axle improved front stiffness. Where I see Benz coming into play is making a set of long-travel, high leaf-count springs that ride smooth, like Deavers. I'm pretty sure Benz would come it much cheaper based on my experience with them.
PS - I'm also running Les Schwab Monotube shocks. Great ride and control. But short life. So about every 20,000 miles Schwab's sticks on a new set (no charge of course). But I'm also running primitive roads with a full load (12,000+ pounds on the van alone) and sometimes at highway speeds. It occasionally catches some air. Sometimes on purpose. But usually not.
2000 E450 dually V10 wagon