Probably the most economic way of making your Trooper "Posi" capable, is to go to your local JY and find a '92-'97 Trooper and check the option plate. Option plate found on the engine side of the firewall, and look for option "G80". The G80 should get you LSD, but check it anyway when you pull it. If you can, turn one rear wheel and if the other goes in same direction, it's LSD. Be sure it is the same ratio as what you have now, which may be 4.77 or 4.56.