height setting for alignment 2001 P38

Does anyone know what the air suspension height should be set to durring alignment (ie,hwy,normal)? From what I have read, most of the vibration/shaking issues seem to happen at hwy speeds. It has the "death grip shake" at 50-60 after a bump. It has been into the dealer and nothing was found wrong with the suspension. (tight as a drum). The dealer said it was the tires. But did not check alignment. The tires probablly are not helping (Mich 4x4's with scalping and worn) The 4x4's from past experience are a really great R/R tire when new. But when worn, are wandering and LOUD. Am putting new Mich's LTX's on it and an alignment. LTX's have worn well on my past R/R's. My 1990 R/R 200K, and Ser III are smooth as silk compared to this 2001 P38. The P38 should be impressing me, but it's not, or my wife. Its her new truck, she's not getting the Classic or my Ser III.
Thanks