If the axle is mounted BELOW the springs in the original set-up. then remounting it ON TOP of the springs, changes alot of things :
...first, you will have to fabricate, and weld on a plate to re-mount the springs to the axle... unless you're an experienced, certified welder, you don't want to mess with welding on a forged axle...
...next, you will have to notch and box the frame rails for clearance, raise the steering box, and modify the steering arms...that's alot of work for only a few inches of lowering!...no one makes dropped spindles or uprights for a beam axle...
You could check around and see if anyone makes a dropped axle for your application, or, have your original axle dropped, but, you will still have to modify the steering arms...
The simplest way, without changing the steering geometry, and doing alot of fabricating, is to pull your leaf springs, flip over the main leaf, (which is like reversing the eye), remove the helper springs, and reassemble the leaf packs, CAREFULLY!!!
This should give you about a 4"-5" drop...check into using a lower profile front tire too...you can pick up a couple inches with that...