zspeed10
+1y
The torsion bars are adjustable at the rear mounts so that the truck can be set level, side to side, at the factory or service shop. You can adjust the rear torsion bar mounts so that the truck will lower. When you do this, the adjusting bolts are loosened, or unscrewed downward. So if you use that adjustment to lower your truck, the adjustment bolt will be unscrewed so far that it will be closer to the ground than your frame rail. If not, it will be close. So instead of laying frame you'll be scraping your adjustment bolts. That will be an absolute PAIN IN THE ASS if you ever need to remove or adjust them again.
So, the alternative is to remove the torsion bars from the front mounting point and reinstall them a few grooves (or teeth) off, resulting in a drop, like mylilpwny did. There is a good tech thread on how to do this...
Your camber will be totally out of spec if you lower your truck without replacing suspension parts like arms or spindles, or fabricating some new attachment points for the stock control arms.
And...just my opinion...a "proper" drop is any drop you want. You have to be the judge of whether or not your drop is safe (for you, other drivers and the roads we all pay for ),is comfortable (can't get more subjective than that!) or looks good!