I think that is a Dexter Torflex torsion axle, and I think there is a lift kit available that will give you more ground clearance. If your 2003 T-139 is anything like mine was, your black and gray valves stick out the back and are at risk of hitting the ground when you are coming on and off of a steep driveway, like in a gas station.
The lift kit should take care of that -- it will give you two inches of additional clearance, which is a lot. Here is a link that may be of help:
Or you could get rid of the whole torsion suspension and install leaf springs and shock absorbers -- we had that done to our new X-139 when we bought it in 2012. We also had them flip the axle for even greater clearance.
Or you could install a true independent suspension -- that would take some serious welding skills. (I wish I knew how to weld.) While you are at it, you could upgrade the axle -- the stock axle is 2500 lb, and you could install a 3500 lb version.
Let us know if you have additional questions!