What part of the world are you in, maybe for a 6pack of liquid refreshment someone would be willing to spend 10 minutes under your van?
The best option in your case is having the springs redone - as you are always going to be heavy - airbags are a better option for people towing, as 10 minutes from now I can shed hundreds or thousands of lbs from my truck. The cheapest option - and a bandaid, but you said you are looking for 10k miles - is what I posted. If you wanted another 50k+, then go straight to the rebuild leaf springs and add a leaf.
