Someone here in the UK has done this to an AD truck. The biggest issue with this modification was that there was very little suspension movement left with the front axle mounted on top of the spring. IIRC, there were clearance issues with the track rod to the springs also.
To avoid having huge amounts of bump steer with this setup, you will also need to move the steering gearbox up on the chassis so that the drag link is still parallel to the ground at your truck's "normal" ride height.
If I was going to lower my truck, I think I would use one of the stretched lowered straight axles instead.
Good luck with your truck, Stuart.
Last edited by Stuart_Giles; 04/12/2010 10:57 PM. Reason: more words added.