Where to start with wdh adjustment for new truck?

500-600lbs on the back of a 3/4 ton?
I'd start by gathering up all the equipment, take a couple nice photos of it and log into Craigslist and place a 4 sale add!

Unless you had inherent sway issues, in which case I'd first pile some more weight up front and see how it acts then. If it's good, I'd replace the ballast with something useful for camping like extra batteries and let 'er buck!