Based on the master parts breakdown for the Limited/Base Crossfire, the springs should be the same.

The rear spring only has one part number listed, 05127493AA

Front is the same situation -- one part number, 05102297AA

If there were different rates, there would be two part numbers per end (or at the very least, in the rear).

SRT-6 springs are different, as they are much stiffer. Same goes for the sway bars -- they will swap from one platform to the other, but they are a bit thicker on the SRT-6.

Aside from the springs and sway bars, the suspensions are the same.

Hope this helps.