BTW.
If you took it to the dealer, and they didn't fix it, take it back and tell them. If it's something covered under warranty it's better they fix it than you messing around with things that might let them blame you to get out of covering it.
If you don't feel like trying with the dealer:
Make sure it isn't a bad shock first. The stock ones are terrible.
If you don't feel comfortable working on torsion bars then don't mess with them. They're loaded springs with lots of kinetic forces stored in them and could kill you if you don't know what you're doing. If you still want to adjust them here are some tips to help.
Make sure your truck is on level ground before you adjust the torsion bars. If you can't find level ground at your house, grab your 17mm, 19mm wrenches and sockets and go find a parking lot somewhere.
Bring a measuring tape. Measure your vehicle height from the front of the frame (near where the rear of the a-arm is). There are more precise ways of measuring this height using a-arm angle, but the frame will do for now. If it's the same on both sides, then it's some other problem, so don't mess with the t-bars.
If the one side actually is lower then tighten the adjusting bolt 360 degrees, 2-3 times. Now you need to bounce the front end of the truck to get the suspension to settle. Check the frame height again. Adjust as necessary. You will reduce the number of turns as you get closer. If you went over, just back off the bolt some more. Make sure your locking nut at the top of the adjustment bolt is tight before you finish.
Don't measure your vehicles height from the body as this will be inaccurate.
BTW, where did you measure to determine your truck is off by half an inch? And what did the dealer say when you picked it up from them?