Deco trucks have "knee action" shocks and leaf springs.
I don't know squat about lowering a truck.. always seemed linda like sewing tits on a bullfrog.. but i'd guess about the only way to lower the truck without cutting on it would be to pull a leaf or two out.
Be warned that if you try and "Slam" it using that method, what you'll likely see getting slammed the most is your tires in the wheel wells.
You'll probably have to end up cutting in some real shocks to keep it low, but not draggin.
If she's all together and sweet and solid, i'd sell it and use the fat cash you get to buy an s10 truck and a less than super clean deco body to slap on it.. lots of "slam" mods available for the s10 family of baby trucks.
