Are you sure it's stock? No add-a-leaves in the back or replacement springs in the front?
A few things can be done, but none of them are going to end up with you having a soft ride. It's an old utility vehicle, and worse it's almost 50 years old now. Leaf spring packs can wear in and "take a set" as individual leaves literally wear into the leaf above them. This locks them in place for the first little bit, but lets them move after a little more force is applied. This ends up not necessarily being "stiffer" but sure makes it "harsher" for sure.
Shocks and tires are next. A good set of Bilstein 5100 series, or a softer shock are a good start. A Rancho 9000 set on a low setting would theoretically help, but I never found that to be the case.
Tires are the biggy for harshness in my book. What kind of tires do you have and more important, how old are they? If not sure, look for the date codes on the sidewall. Should be near the DOT label.
paul