Personally, I'm not a big fan of lift/lower blocks, shackles, and things of that nature. I used to be into the lifted 4WD scene (not street queens, ones that actually got used), and most of those guys frown upon blocks and shackles because they tended to create problems, either through weird geometry angles or simply weakening the suspension system. That being said, most of those guys are pretty hard on their rigs, too. If you are fairly easy on your ride you probably would be fine with extended shackles. I'm just looking at the cost of the shackles ($70) deducted from the cost of the springs. That's $260, you get the drop you want, and non-wavy springs to boot! At the end of the day it's your decision, good luck with whatever you choose.