I didn't bother to read all the replies, but in case no one has said it, I will. Lifting a KDSS equipped vehicle is not possible, running 285/70's will not work, body lifts are for Heeps, what you really want is a Subaru.
But seriously, 3 inch lift can be done. I did it without spacers or any recalibration of the KDSS. Obviously, paying particular attention to the wires for ABS and disconnecting them and not stretching / damaging is the larger concern. Putting the sway bar (front) back on after the lift is a PITA, but it can be done solo. The truck will handle amazingly for a lifted vehicle with the KDSS. Body lift if not necessary for 285/70's. I am running 285/75's (34") and had to do the BMC, which would be the bigger concern and pounding the pinch seam flat. The lift and KDSS will impact the travel on the rear suspension. I have found that it DOES (despite what other may say) impact up and down travel. I have disconnect my KDSS and can say from first hand experience that this TRULY is the case. IF your not hard core wheeling, it will be a great set-up.