If I recall correctly, the TJ springs are about 12.5" long. Here's a quote from a Jeep forum regarding the "guesstimated" spring rate for each type of spring...

"There are four different versions of the springs that were used from 1997 through 2006. These are the ones that can be used on the C10. Similar rear springs could be found on the Jeep Grand Cherokee ZJ. All four versions are the same length wise but vary in rate.
The only way to tell them apart is by the color coded tags that are on the springs from the factory, they read as follows:
103AA (or 3AA) 130lb.
104AA (or 4AA) 140lb.
105AA (or 5AA) 150lb.
106AA (or 6AA) 160lb.
The colors on the tags can vary and the rates are "ball park" at best."

Hope that helps... <img src="/forums/images/graemlins/kewl.gif" alt="" />

1997 Sportage 4x4, auto-trans, Warn manual hubs, 4" UPYOURKIA front lift, TJ 106AA rear springs, 2-5/8" body lift, 31x10.50 treads, SmittyBilt SRC front and XRC rear bumper, swing-out tire mount, OBX LSD front diff, Track Finder rear locker, 5.38 R&Ps and... really crappy gas mileage! <img src="/forums/images/graemlins/shiner.gif" alt="" />