Thats not a verry god fix. A shackle will only make 1/2 inch of lift per inch of length added becouse you are only lifting half the spring. I would say that spring wrap is probably what is killing your springs. The best long term fix would be to buy a better spring pack, and possibly a anti wrap bar. If you do try to fix the height difference with longer shackles, be aware it could effect your handeling. I don't think any manufactuer would sell ya a mismached set of shackles.
