You can leave the Magnum flex plate, and depending on what transmission you're using....you may have to oval out one bolt hole where the torque converter bolts up. I think this is the case of you are using a 904 or 727. A 5.2 flex plate will not have weights welded to it, and a 5.9 flex plate will. The weights for Magnum 5.9's are on the flex plate instead of the converter like LA 360's. You use a neutral balance converter with either a 5.2 or 5.9 Magnum.