Now when you say "bouncy" do you mean stiff? All that can go wrong on a leaf spring is they break from over loading or they flatten out over time. That makes them a little softer. There is not much you can do with out changing springs. You can always take out one leaf. That will give you a softer ride. You just can't cary crap in the back. To check them all you can do is mesure the arc of them. I know that my truck has always been stiff. In fact I even went and had a leaf added to the rear so now I have 3 full leafs in the rear, and new over sized coil springs that were 1.5 inch taller on the front. Now it’s real stiff. Nearly rock hard. Now when cornering the rear will come loose before the front will. Now with almost nearly every car out there on the road today they "push" in the corner stock from the factory. If you go hard into the corner they want to go straight and not make the turn. If you stiffen up the front then you can corner harder. If you go to stiff you can create an “over steer” and the back end will come around on you nearly every time you get into a corner. What Nascar does is real simple. To build an adjustable front spring you need a large bolt about 1½” dia. by about 8” long. You weld a plate to it and put a cage on it. That’s it. See the pict.
The spring is missing. To stiffen up just crank down the adjuster. Now for the rear on a truck you can order springs to a weight load. Our trucks have about a 1400LB rear spring. If you want a smooth ride go coil over with control arms and a pan hard bar. I had the opportunity to work on Winston West cars and some Nascar Cup cars when working for Coca Cola. Here is Jack Sellers website.
http://www.jacksellersracing.com/ He is one of the owners of Sacramento Coca Cola. Better known as back of the pack Jack. I worked for him for over 7 years. The car that I manly worked on was one of Ricky Rudd’s old cars. Jack picked it up after one season on the track. It was eventually stolen by a guy back east that was working on the car then went out of business and disappeared along with the car. Here is what it looked like when I first started working on it.
Under steer, over steer. Sorry it's been 18 years since I worked on Nascars. This is why I own a ready mix company now. It's easy now. I point, and say you,, go deliver concrete. But I still work on the trucks and tractors and drive them when nessary. You just responded to quickly i was still editing. I would have seen it sooner or later.