You might want to go through the archives on this. As I remember, most were not as impressed with it as a true 'fix' of the problem, esp. given the cost.
I'd bet the source of the clunk is from a worn track bar (assuming this is a 4x4, as you didn't say either way. ) I felt mine through the steering wheel when turning say into a driveway over a bump. Also some years, maybe the '97s (can't remember) had a TSB on this issue that centered around the shaft bearings in the cab. Again, I'm not 100% on this, maybe someone else can give more detail.
You can check the steering shaft by grabbing it and yanking, also watch it at the u-joint as someone inside is moving the wheel right to left. If it is ok, fire up the truck and have your helper do the same as you look at the track bar ball joint. I could visibly see the play in mine, and that was only after 20k miles.
If it is the track bar, upgrade to a DT or Lindstat to eliminate the problem.
Hope this helps.