Shaftmaster, not to question what you did, but did you upgrade the torsion bars when you removed the the air shocks? The reason why I ask is that the full air ride suspensions have a different torsion bar than rear air ride and non-air ride vehicles. The 4 wheel air ride suspensions have weaker torsion bars to allow the air shocks to carry some of the load. So, if you didn't upgrade the torsion bars or install the coil over shocks, then there is your problem.
As for the torsion bars, yes, they are the same between the Navi and the Expy. Get the torsion bars for the same year Expy without the air ride suspension and you will be golden. Just a side note, the F-150 also uses the same torsion bars with an exception, the Supercrew. The Supercrew uses a slightly shorter torsion bar than the others, so, if you find one in a junk yard, you should be good unless it is a Supercrew. May want to measure the length to just make sure. Not sure if it is the same torsion bar from 97-08 or not. But, if you stick with the same generation, you will be good.
