A radial willy typically have a stiffer sidewall than a bias drag slick so you should have less rock from the sidewalls with the tire you are running. you should also pull the bolts out on the locator and the front mounts to make sure that the bolt has been eating away at the brackets because the bolt is to short. If the hole is oblonged then that will cause exactly what you have going on. The "kit" ladder bar and 4 link systems typically have too short of bolts in them. The shoulder of the bolt should go all the way through both sides of the bracket and use washers to keep the nut from bottoming out on the bolt before everything is tight.