[ssgharkness020147]

The Rubber Duck suspension lift is not 4 inches. They are a set of spacers that will give you 2-3 inches of lift depending on how heavy that particular truck is, and the condition of the springs.

The stage II kit includes a 2 inch body lift as well which is where the four inches of lift comes from. Go to Rubber Ducks website to see before and after pics of a lifted truck. With that kit you can safely fit 42's, but you will need to re-gear the diffs and or trans to be able to run them (practicaly).

As far as the geometry goes, yes it is altered. The kit includes "shims" for the ball joints to correct the angles of the ball joints, but the springs and control arms angles do get altered a bit. A decent number of folks are running the Rubber Duck lift, love it, and have not reported any problems because of the geo change.

IMO anything over 40's will require a re-gearing, I'm going to 39.5 Iroks soon with a lift. I'll let you know how much slower my truck is after its all in.