Long shackles help the rear drivetrain angle, but in my opinion long shackles make them easier to hit on rocks. I have 2 inch extended shackles and I think that I will hit them much sooner than my old stock length ones. Blocks greatly increase axle hop/wrap, but 3 inch blocks are not uncommon, in fact I used to have 3" blocks on my truck. Most of the lift companies use blocks up to 3 inches for the entry level lifts.
If you are using your truck from normal type use and not trying to do the difficult type trails I would thing that you would be ok. It all depends on the condidtion of you springs.
