If you just lowered it by the torsion bars up front, raise it back up. Then get some good drop spindles. This'll bring you down a couple inches while maintaining some ride comfort. If you do decide to go lower by adjusting the torsion bars, remember that having the drop spindles will keep a higher amount of suspension travel opposed to having the drop with torsion bars alone (at the same ride height).
So you'll probably be bottoming out the truck before bottoming out the suspension if you go too low, pay a little more for "high performance" shocks and you can noticeably reduce this occurrence.
Say goodbye to the exhaust pipe under the cab. You will hold up traffic at even smaller speed bumps.
And if you do decide to just max out the torsion bar adjustment, hopefully you have insurance that'll cover chiropractic attention, and a connect on tires.
As for the back, I have 4" blocks, and this along with the front has my frame crossmember under the cab 1 1/2-2" from the ground. Can't go much lower before cutting shit up.
If the streets aren't falling apart in your area, it ain't too bad. I'm not into bags, but it may just be more practical if you want to "slam" your ride.
EDIT: And like filthy said, notch it if you go any lower.