Softer ride on a '98 Taco?

I have a '98 2.7L 4WD with a 3" lift. It's been a great truck, but one of the few things that bothers me is the ride, primarily in the back. It's a light lifted truck, so I'm not expecting the ride of a Jag, but I've noticed when I go over a bump, the front takes it just fine but when the rear wheels reach it, it jars the whole truck as if there was no suspension. The owner before me used it to haul firewood, so I suspect he may have changed the leaf springs, but I can't really be sure. I put new Skyjacker shocks in the back not expecting much and it didn't change anything. Anyone know of any good soft ride leafs or anything else I could do?