It all boils down to the way he's got his rear four-links mounted. Causes the rear end to tuck under rather than pop up as you see other trucks do. He also had a set of sway bars on the truck that didn't react the way they're supposed to. That may be part of the "throws its weight around in a weird way" you were referring to.
RKM, the shocks are standard Combs triple by-pass.