When I had my truck lifted I could only gain an inch by adjusting the stock keys before I ran out of adjustment. I ran it that way for a couple of weeks and found the ride to be very bouncy and "floaty", after I installed the lift keys I gained another 1 1/2 " and the ride firmed up considerably and in my opinion performed much better than stock. The stock shocks are good on a half ton truck with up to 2 1/2" lift. As previously stated each truck performs differently depending on the spring rate of your torsion bars. I say go ahead and get under there and start cranking, you're not going to hurt anything, you'll probably find one bolt is already turned in further than the other, so just count how many turns you put on that bolt and adjust the other one to match. I'd just go ahead and turn them up as far as the shortest bolt will let you and go from there. Here's a list of the different bars and their ratings, I have the YT bars in my truck, If you have the same bars you'll probably get the same results.
Part#
15048307-LH (code XK) (Max torque 4553)
15048308-RH (code XK) (Max torque 4553)
15048309-LH (code XL) (Max torque 4626)
15048310-RH (code XL) (Max torque 4626)
15712407-LH (code WX) (Max torque 4863)
15712408-RH (code WX) (Max torque 4863)
15048311-LH (code XM) (Max torque 5638)
15048312-RH (code XM) (Max torque 5638)
15058267-LH (code YH) (Max torque 5913)
15058268-RH (code YH) (Max torque 5913)
15712409-LH (code WY) (Max torque 5913)
15712410-RH (code WY) (Max torque 5913)
15528957-LH (code GG) (Max torque 6709)
15528958-RH (code GG) (Max torque 6709)
15712411-LH (code WZ) (Max torque 7267)
15712412-RH (code WZ) (Max torque 7267)
15072933-LH (code YT) (Max torque 7267)
15072934-RH (code YT) (Max torque 7267)
15528963-LH (code GK) (Max torque 8615)
15528964-RH (code GK) (Max torque 8615)
15528965-LH (code GL) (Max torque 8782)
15528966-RH (code GL) (Max torque 8782)
15732338-LH (code XG) (Max torque 9054)
15732339-RH (code XG) (Max torque 9054)