I bought a set a 3.5 leafs and I already have shackles. I want just a little more lift out of it and I have a set of helper springs. Can I ad them to these?

 

You can but the down side is the springs will be stiffer and most say adding a leaf will make the springs sag faster over time.

 

In your post you state that you already have shackles, but not whether they are stock, or if they are lift shackles, or how much lift if they are lift shackles. It would also be good to now how much lift you want to end up with, like 4 inches or 4.5 or 6 it makes a difference in what you use to get there.

 

You do realize there is ALLOT more to lifting mopre than 3" than just taller spings. Like Trackbars, control arms, driveline issues, ECT.
Helpers don't usually lift any more than the thickness of the Helper spring spring, but yeah you can add them.. They will definately limit your upward flex.

FWI- AAL do not cause sagging, BUT they will sag to match the sag of the springs they are added too.