73 Dart Leaf Springs

Hey fellas;

So I installed new leaf springs that give my 73 Dart Swinger that Stink Bug look, it's about 2.5 Inches higher in the back. My only problem is that when the car is going over a bump, on the way down the bump, there is a loud banging sound. I am thinking it is the leaf springs returning to their original position before going over the bump and springing back. Would I need new shackles? Should I do away with the shackles completely? I don't exactly know how I should fix this issue, so any guidance in the right direction would help. Thanks in advance.
Are your shocks long enough? They could be going to full travel and banging. -Jed.