i was searching some forums and i found a couple of links that said a helper/overload spring would help with the saggy rear and bring it up about and inch is this true and what style should i get?

 

i think some of those helper/overload springs go on the very bottom of the pack and are much flatter than the rest of the leafs. the problem with that is that when your offroad, there could be a good chance of getting that leaf stuck on something and ruining your day.
depending on how flat your leaf pack is, it might just make more sense to get new packs or make your own.