I would go for the packs. Your spring is set up so it has a long and short side. It is also angled with the long side higher than the short. Engineers who are smarter than me set it up this way to be able to provide a longer spring on one end and improve the ride over a level spring. When you use an extended shackle, it lowers the rear of the spring and puts a more equal load on both sides. The longer side will flex more. Lots of guys like shackles for this reason. But it causes the rear of the spring to flex more than the front under full stuff and will eventually take the temper out of the spring if used hard off road. I would rather protect my investment with the full pack minus any shackles.