Ditto what Roppa said and I'll add this; Mopar springs are also wider which provides additional roll resistance as the body tries to twist the spring in its mount. At 2.5 wide this is a much stouter design than 2 inch Ford or Chevys.
They are also not mounted parallel to each other. The fronts of each spring being closer together than at the rear.
This is true of E bodies and F bodies only. Post 73 B bodies are actually splayed the opposite way being wider in front and narrower in the rear. Pre 73 Bs and As are all parallel.
Super Stock springs are a lot stiffer than the factory ones which could be why.I am getting mixed responses to using a snubber with the SS springs as well over on Moparts.
I'm not surprised. If you think about the action an SS spring imparts, it actually renders the snubber useless and the tuning is all done with spring clamps. SS springs work be creating body seperation from the suspension and forcing the tires into the ground by using the body weight as leverage. As this seperation occurs, you are also putting distance between the snubber and the floor.
The problem with "slapper bars" is they hit the leaf spring in the wrong place.
IMO, this is one of the biggest problems with slapper bars. Contact point is critical to their success as the wrong contact point can bend the main leaf. Since the vast majority of slapper bars are universal, most are never set up correctly. Additional drawbacks are; twice the weight of a snubber since there are two of them, and lowered ground clearance which can create havoc on a street car. Snag a speed bump or some other road irregularity and you may bend more than just leaf springs.
