All a set of stiffer shocks will do is make the ride harsh and beat up whatever cargo you're hauling. If you want more stability in turns, install a rear anti-roll (not sway) bar. It's a U-shaped bar that attaches to both frame rails and to the rear end at the spring plates. It allows unrestricted up and down motion of the rear end when hitting bumps, but it restricts body roll in a turn. Heavy duty bars front and rear will add stability without making the ride rougher.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!