[robnolimit]

That brings up a good point. Springs vs. spindles. Lets start with the concept of a stock truck. If you put a set of 2 1/2" drop springs, the truck is lower, and the Roll Center changes (lower) a lot. Looking at the next drawing, first you need to understand the Instant Center. This "point" is the connection of two lines passing through the ball joints and A-arm pivit points. The I.C. is the point at which the mass of the truck rotates to push on the tire in a corner. As you lower with springs, the I.C. of each side drops.
Next is to understand the Roll Center (very important) The tire is grips the ground. So, the force line, or direction of push, on the tire, is the line from the I.C. to the center of the contact patch of the tire. The point where the two lines cross is the Roll Center. Natural "body roll" (without swaybars to control it) is created by the difference from R.C. to the Center of Gravity. We can estimate the C.G. of these trucks at about 2" above the cam shaft. The farther the R.C. is from the C.G., the more body roll, = less traction. There can be some positve benefits from shorter springs, such as more agressive camber gain, but once the lower ball joint is higher than the lower A-arm pivit, your loosing ground. In casses of really short springs, say 4"+, it is easy to have the R.C. under ground, not good. The goal is to get the R.C. as close to the C.G. as you can. When you drop with a spindle, the R.C. is not effected as much as when you drop with a spring. Just a note, Z'ing the frame up, - or - raising the crossmember may be the best aproach for handling in these trucks, as you get the lowering (lower C.G.) without lowering the R.C. - food for thought.