When I restored my Challenger RT four years ago I had the rear springs re-arched. I soon found out I wasted my money as the springs soon settled back to their previous level. I always thought the rear was about one inch too low but had read on this site about some of the new springs not being too great. Finally, after reading new posts and opinions I ordered a set of ESPO stock height springs with 5 1/2 leaves and 1 1/2" front bushings. They arrived last week and I installed them the same day, taking only two hours time. The new springs raised the rear bumper one inch and I like the looks much better.
The ESPO price was very reasonable at $220/pair but shipping was 1.00 per pound or $86.00 to my door. Nevertheless, I'm now happy with the ride height.