That is exactly what Dvorak said....they sound like station wagon springs. Could it be that they were made wrong at the factory? The part#'s stamped in the springs match with the springs Mopar calls out for a 3600lb. E-Body?

Not sure if it's still for sale but:
http://www.cuda-challenger.com/cc/index.php?topic=67321.0

"Its all new i have the mono drop springs/adjustable shocks/caltracs everthing you could buy from calvert to make a e-body hook..I jumped the gun a little to quick when i bought it cause i want to make my car a touring car and this system is for street/drag racing...i would like to trade for a set of drop springs and what ever i need to get my car back on the ground..also has the offset brackets to move the springs in and i have a b-body rearend under the car..here is the pics...lets talk"