Measure , mark w/white paint pen all the way around the axle tube.....then grind them off, put rear in , slip new pearches under...toss the u bolts on loosely...adjust rear side to side and roll to rough in the desired pinion angle.. then snug u bolts and set it down and measure the pinion/yolks angle with driveline in place. Reverse steps and adjust as needed, torque and spot weld..., lift car and remove u bolts out of the way and finish welding. The pearches have locating holes for spring nips to closely dial in the to n fro for each side, close enough that with a tape you can dial the last 1/4 or so in. If that's not understandable, sorry that's all I have time for right now.