I couldn't get an answer on that either (at least not from anyone who actually knew). Consider this: at the back there is only one way to do it and that is with springs. At the front there are three ways: spindles, spring perches or springs. Given that when I changed out the springs I got one more inch of drop (just as I expected) I will state categorically that the XFE is a springs-only job. Actually, from a part complexity and interchangeability perspective, any other approach would be crazy. As further confirmation, when they did the SS version of the Trailblazer it was a simple spring cut (exactly one coil - everything else was identical).