Suspension advice

First off in handling upgrades would be a good set of tires. As they are the only thing connecting your car to the road. After you have them you can concentrate on making them perform the best they can.
The other upgrades you will "feel" the most will be as follows and why.

Anti-roll (sway)bars- Because if it feels like your going to flip the car over your not going to want to drive it hard. Also it keeps the tire in contact with the road by controlling the roll so the tires don't get positive camber(tire tipping over) so the tire can stay as close to flat as possible therefore getting the largest contact patch available and maximizing available grip.

Bushings- Are what keep everything in alignment. Small changes in alignment are VERY noticeable while driving and can make your car feel like its alive! And not in a good way. A good set of poly bushings will keep all the suspension attachments where they should be. Stock rubber will deform under hard cornering.

Shocks- are what actually keep the tires in contact with the road when your going over bumps. they damp the up and down motions so the tire doesn't bounce up and down like a lowrider with a set of hydraulics. The compression/rebound settings of the shocks will affect the fore/aft weight transfer (drag shocks maximize transfer road-race type minimize).

Springs (and torsion bars)- Will help more for the fore/aft movements like accel./braking forces. however A-bodies have a large amount of anti-dive built into their front suspension so braking forces will not affect it as much. Rear leaves should have some amount of anti-squat built in so it will keep the weight from transferring towards the rear too much. Also the compression/rebound damping on the shocks will affect this(see above). Spring rates do affect roll stiffness but they also affect vertical(bump) stiffness. so they will penalize ride quality and suspension travel. Most experts recommend Soft springs & stiff anti-roll bars for street driven cars. although stock mopar spring rates are Really soft.

Hope this helps!

Benjamin
(Bjkadron)