Things you can do
Couple of things dude. You could get some heavy duty helper springs and try them out, like $25/pr, they'll add around 1000lbs to your load and if they aren't enough for now, it's not much lost at all. If you can weld, you can put some bumpers, i.e. steel bumpers between your axle and your frame that will stop your truck from sagging when you hit a certain point. Both methods work well. I use an old 91 Jeep with 180,000 miles on it to haul my wood in a 67 ford 3/4 ton box that has been modded to a trailer. I usually put between 1 and 1.5 face cord in it easy. I'd put more, but no real need to. The old Jeep has a 4.0 and has no problem pulling around 2 ton. Hope that gives you a couple ideas dude... Also, before you go spending a ton of money on other stuff, check out pricing for a used trailer to haul your wood in. That way you'll only be using your truck to pull it, not carry the weight...