Can I lift the rear with shackles?
Shackles are for Chevys. Mopar geometry dictates that the spring will just flatten out.
This is correct in that the stock springs were designed to have little or no camber under light loads for better handling.
I have page 169 of the MOPAR chassis manual in front of me by Larry Shepherd which states this.
I have replaced E body rear springs with MP springs with no effect.
The springs were still flat as they should be.
Lesson learned.
SS springs are for a different purpose like you said, I think.
If the rear of the car is made stiffer it will increase overseer which is undesirable .
Conversely the front end can be made stiffer to increase understeer which is desirable in a street application..
I have replaced several cars with junk yard factory LC arms and factory sway bars for this purpose.
The handling was improved.
Somewhere I remember reading that only AAR and TAs came with arched springs for exhaust clearance. But I can't be sure of that at this time.
I have added springs from junk yard M bodies with good results.
Not to lift but to decrease travel under load.