Does your truck have secondaries? (the so-called, separate upper overload springs) If so, consider Stable Loads or a facsimile.
Does your truck have a thick lower overload spring in the pack? Again, consider Stable loads for the bottom spring.
I would check into a thick slight lift (2") spring for the rear. You may have to get longer U-bolts.
Also, a thick gauge, anti-sway bar on the rear will help keep the load from swaying in corners, athough off-road it will be a nightmare unless disconnected on one side.
I think it's all doable, although with a 1 series truck you will be close to the edge. A lot of people have made this combination work just fine.
jefe