There is a torsion bar write up over at
http://www.planetisuzoo.com/articles.htm?id=117 that talks about lifting, same idea just you are going the other way. One thing it does not mention is that you want the truck on jack stands or at least put a block under the frame some that it would catch the truck if something breaks. If the adjuster bolt broke with you under there, the truck would come down hard, fast, and very low. Not that there is a big chance of that, but I've broken one and even with a block there to catch the truck it was not fun. Start with spraying the bolt head and the adjuster block it threads through above (t-bar has a thing that sort of hooks under it) with some penetrating oil. Might as well do that right away, give it a few days to soak in.
BTW, I believe it follows the old rule "Righty Raises, Lefty Lowers".