Mopars have a super short leaf spring compared to the Chevys. The hit and unload, often called porpoising, is common to the Mopars for this reason. Lil bro's car was awesome till we put the stroker in it and then it started the same deal as your friend. The answer was a good pair of double adjustable shocks along with a pinion angle change. Check the angle first cause thats cheaper than a set of shocks. You should have at least 5 degrees on a leaf spring car and it is absolutely critical on a leaf car.