Jack car up and support with jack stands on the frame in front of the spring hanger. Use the jack to support the rear axle. Do one side at a time. remove tire, remove lower shock from shock plate, remove U-Bolts holding axle to springs, remove rear shackle. Geting the rear shackle out of the frame/spring can be difficult if it has the original rubber bushings (be prepared to replace them.) Use a prybar to pry the shackle out of the frame, be careful, the spring will drop to the floor once the shackle is free from the frame. Remove the front spring hanger (4-nuts), and pull the old leaf spring out. Remove the front spring bolt from the hanger, and swap the hanger and bolt onto the new spring. Make sure the hanger is oriented correctly, the lower bolts on the hanger are narrower than the top bolts. The front spring bolt goes in from the frame side so the nut it to the outside of the car. Put the new spring back under the car and bolt up the front hanger. The rear bushing hole in the body will probably need to be cleaned up before you can install a new bushing. Anyhow, install the rear frame and spring bushings, and install the shackle. Replace the U-Bolts (I think stock U-Bolts are 7", Mancini racing has them), and tighten the shock plate back on,and put the shock back on. repeat on the other side.