Originally Posted by Andrew Gibbens
Ooowww, turning a drop axle upside-down is a scary idea.
If you did that, the only thing holding the axle in position would be the friction in the U-bolts holding it to the springs. One big thump, like driving over a rock, might just rotate the axle backwards. With the axle suspended below the springs, it would also have a lot of leverage to twist the springs into an S-shape on braking.
I strongly agree with Andrew - this would be extremely risky, as dropped axles are not designed to work upside down for exactly the reasons mentioned. Spring/U bolt failure and suspension collapse would likely be the eventual result.
In addition,you cannot simply rotate any trailer axle, dropped or not. All trailer tube axles are cambered (bent up in the middle) to maintain reasonable wheel camber under load. The result would be excessive negative camber (wheels leaning in at the top) and heavy wear on the inside of the tires
What you have now is the original 3500lb 4" drop axle that has been converted from underslung to overslung (springs on top of the axle). If you need even more clearance, the best solution is to install an overslung straight axle as Bob recommended. Springs, bushings, shackles and bolts should be replaced as well. I think you will find it more economical to replace the complete assembly rather than buying individual parts.
I also noted in your photograph that there is no bump stop installed to prevent the springs from over deflection. Dexter recommends that one be installed on all overslung installations as spring bending or failure is possible. There should be no more than 2.5 -3" of available axle travel when loaded according to their engineers. There is a lot good information available at; http://www.dexteraxle.com/products___literature
If you are mechanically inclined, a complete spring/axle replacement is a pretty straightforward, simple bolt on job. Axle alignment will be required, but only involves loosening the U bolts and moving each side of the axle back and forth until the ends of the axle are equidistant from the centerline of the hitch. If you are at all uncertain about your abilities, have the axle professionally installed.