Even with the Hellwigs, you 'should' not over load the trucks GAWR, which will be in the neighborhood of #3500. I've got the LP-25's as well, and while they are great for keeping the truck pretty level with #1000 payload, they are still attached to the stock leaf springs.
I'd only haul 1 yard at a time. Better to make two trips to the yard, then one trip with two yds and the other to the shop to fix whatever broke!
I've got a small utility trailer with a payload cap of #1500. I'll usually put a yd in the bed and a yard in the trailer. Wow, instant F250 payload!
