Lifting by the diff will keep the springs compressed making them really really really really really difficult to remove.
However, you could lift it at the diff, place jackstands under the frame rails and then lower the jack to drop the diff to full droop (after removing the shock bolt). Then the the springs will drop right out!
yah! thats what i meant.. just forgot to add in the part about lowering the jack after placing the jackstands
"Engineers believe if it ain't broke, it doesn't have enough features yet"