I have found tires make a big difference in the ride of the truck, if you are running an old style tire like 6 ply's try something like a 85 series car tire. Keep the pressure down around 28 or 30 lbs. be aware it makes the steering very hard to turn.
You might also try removing one or two leaves from each spring. This will lower the truck a little, so you may have to shim under the spring to maintain the height you want.
Also don't use some super heavy duty shocks, stick with regular garden variety light duty units.
