You remove shims if the camber's too positive, add them if it's too negative. If you lift the front end with the stock UCAs (T-bar crank only), you end up needing a fat stack of shims to get rid of the negative camber. My understanding of the lift arms is that they're a little longer than the stock arms to reduce the number of shims required. If your truck isn't lifted (or isn't lifted much) and you've got lift arms on it, you may need to lift the front end before it'll align. Mine is pretty near stock ride height, with stock arms, and it didn't take many shims to align. I'd have to check but if I remember correctly one side's got no shims at all. If I fitted longer UCAs, it would not align unless I cranked the ride height up to what the lift UCAs were designed to work with.
If you're running a 3" lift and no shims behind the driver's UCA spindle, and it's still got positive camber, I'd measure the arms against each other (from the ball joint to each of the bolts going into the frame) to see if one was built wrong.
And no, you don't adjust one torsion bar to change camber. That'll just make it crooked. Adjust both bars to get the height where you want it, get it level, test drive and readjust as needed because they settle, then adjust your camber.