Its not a big deal to move them. You can get replacement spring pads from most venders or even your local trailer supply house. The only two problems you will run in to are, keeping them centered side to side, and setting the pinion angle correctly.
A good way to set the pinion angle (truck needs to be together, with full weight on the axle) is to bolt the rear axle in place with out welding the pads to the axle. Then using a angle finder gauge,(Harbor Freight) set the pinion to the correct angle then tack weld the pads to the axle tubes, remove the whole unit and finish the welds. This would also work to center the axle side to side.
The original pinion angle and your truck will most likely be different. Check past post on this site for pinion angle information. The simple answer is, set it at the same angle as the transmission tailshaft. A example would be, if trans is pointed down 2 degrees, the the pinion should point up two degrees. Rear some more information on the 4x4 sites and driveline sites.
I use a cut off wheel in a hand grinder to get the old pads off if I going to reuse them. You can torch them off if you have new ones, just stay clear of the axle tubes when torching!
If you are not sure of the past life of the axle, now would be a good time to open it up and clean out all the oil and sludge. Pull the axles and head out to the car wash and really give it a good cleaning. Spray the gears down with WD-40 when done. It will be a lot easyer to work around once clean, plus less of a chance of a oil fire from welding. Joe
