I just did front and rears on my '91 last weekend. As I recall the '91s had the standard shocks and the Sport/Power package which utilized an electronic ride controlled shocks that would be either in a "touring" soft ride, or "sport" firm ride. Mine did not have a self leveling feature but did have the electronicly controlled shocks. And after 144K+ they were shot. Who would of thunk it???
OEM eplacements were not going to happen on mine too much denario. Since I don't do alot of off-roading I fitted new Monroe Sensa-tracs on front and rear. I like them alot, firm but not super rigid. I guess it all depends on your application. Total replacement time was about 3 hours for all four. I consider myself mechanically inclined but I don't get many opportunities to sharpen my skills, not that replacing shocks is brain surgery. A can of PB Blaster, and impact gun,an air ratchet, a two foot pry bar and torque wrench and your good to go.
Mike