Just to add a bit more to the information posted here...
If you don't haul loads in your truck, you can get by with the 4-leaf spring pack in the rear. The 5-leaf spring pack includes a overload spring. I imagine the 4-pack and 5-pack leafs will 'roughly' ride the same. In the meantime, if you're bottoming out in the rear, then you can cut out the bump stop and install a button snubber.
Your long-term goal for a dropped stance shouldl dictate the components you should use. If you plan out your drop, you'll lessen the amount of $$$ it takes to get to your overall stance by buying the 'right' parts the first time around (as funds allow). Of course, it always seems that once you lower the stance, you'll end up wanting to go lower.
BTW, drop spindles retain the suspension/steering geometry better than drop springs.