Check with your axle manufacturer. Dexter Axle has a kit to move the axle from above the springs to below them (I will be doing this when the snow melts (April or May in this area). Other manufacturers may have something similar, or instructions to have the spring mounts removed and re welded.
Even though the process is commonly referred to as "flipping" the axle, it doesn't actually change the orientation of the axle, only its location in relation to the spring. Most axle's built for high loads have a built in crown or bend in it to compensate for the flex under load. If the axle were to be rotated upside down ( to line up with the spring brackets), the flex added to the crown would cause excess camber on the tires.
If the axles are already under the springs, they can be lifted with blocks and longer u-bolts.
Basically, what the last 2 guys said, but with a little more detail. I would recommend checking out your axle manufacturers website, if they have one. That's where I found the kit for mine.