If you put shackles on stock springs, it's only going to get worse.

I leave the main leaf bolted in, support the body on stands, take the wheels off, leave the jack under the axle, and remove the shocks at the bottom. Remove the U bolts. Lower the axle, put c clamps on the spring pack, cut all the hardware off, clamps and center pin. release the c clamps, lay the pack on the ground, keeping it in order. String a new center pin in the pack, add leaves, put the pack back on the main leaf. Use your knees to get the nut on the center pin, then use c clamps to draw the pack together. Once the pack is all straight, beat new clamps on where the old ones were, tighten the center pin, and cut the excess off of it. Repeat on the other side, put your shocks and U bolts back on.

Takes about three hours. I've never changed my shackles and I run 4.5 inches on all mine.