Are you saying you are able level front to rear by raising the front 5.5" by cranking up the stock torsion keys? (I wouldn't think this possible). If you are, no wonder you are experiencing a harsh ride and this is NOT advised. You will be changing the front suspension geometry and putting a lot of stress on the UCA ball joints (UCA = Upper Control Arm) among other things.
Read
<THIS ARTICLE> to get some insight to the geometry of the GM front suspension. This doesn't really apply in your case considering you've already lifted your ride, but it will give you an idea of what happens when you crank your torsion bars.