For the most part I think I would agree with bigtime...However a 6 leaf pack in a short bed & short, stiff sidewalls may really be just too much spring rate. I'd do as he suggested, take out the shocks & carefully drive it on some local roads at relatively slow speeds to see the effects. If it is soft & bouncy...then it can be controlled with shocks. If it's still stiff, but bounces a couple times after a bump, your springs are too stiff.
If it's soft, I would get a pair of Rancho RS9000 shocks (Chris is a vendor for them

) they have an adjustable knob to set compression.
If it's stiff, I would remove one or two of the leaves until it is soft. You don't need 6 leaves unless your doing some 1/2 a ton + hauling often/far.
As to the "sitting level now"...If you take out a leaf or Two & it's lower in the back, it just means, you didn't lower the front enough!
You can easily end up with the same problem going to coil overs, however the height for a given spring rate is usually adjustable.
Good Luck, Lorne