Has the ride height been set and has it been aligned? The springs do settle after awhile. Where did you get the springs? Also a local shop can rearch your springs for around $100.

56 Plaza 63 D100 step side 67 Coronet, 68 Roadrunner, 69 Super Bees, 69 Coronet 500 convertible, 70 Roadrunner Post, 79 D150 360, and a severe case of Mopar a,d,d