Shackles or leaf packs?
 

What is better, stock leaf packs with extended shackles or stock shackles with 3" leaf packs?

Would depend on what you want to do with it. If it is a 90% DD I would go with the leaf packs. If the stock springs are in good shape and it was going to be mostly a wheeling rig I would go with lift shackles it would give you more flex. Most of the time though you would use, say a 2 inch leaf pack with a 1 inch shackle lift for the best flex.