Got 'em, and love them so far, although I haven't wheeled the X hard, and it's back at SLR getting tweaked. They're 2.5" and much stiffer than stock, but they absorb whoops and potholes like they weren't even there. They did require new mounts, etc. As far as I know, there are no Kings ready to bolt right up.
Soon, I'll post the rates, valving, etc, when I know the figures. Also, my qualitative assessment of ride quality. I know the shock we're going with in the rear is 9" long; 10" limited up travel too much.
King's reputation speaks for itself. I know some of us debated name recognition on a thread here recently, but when every other race truck runs something, well, the conclusion is obvious.
Feel free to PM me, and I can elaborate.