Upon re-reading your post, you didn't say anything about smooth ride, only handling. Hmm. Do the bushings, kingpins, and shocks first. Before you tear it down, look at distance between the axle and frame (suspension travel). If there's not much clearence, then the springs must stay pretty stiff to avoid bottoming out on bumps, right? If you have some decent clearence (4-5 inches?) then a softer spring pack might be nice. Pulling half the leaves sounds like too much to start, though!
May also want an anti-roll bar for - well, maybe both ends?
Don't forget the rear end for shocks and etc.
regards
Jay