Were the rear frame rails on the car replaced? And if they were did you replace them with stock plymouth frame rails? I believe (am sure) there is a difference between dodge and plymouth frame rails as far as rear spring mounting locations. The front hanger is also different but that would move your spring location back, not forward if you were using front hangers from a dodge. So I wouldn't think that was the problem. But if you replaced the rear frame rails this may be something for you to look at. Just my Scott