GM-51246 is required on 2013 model year 1 3.0L diesel engines when removing the head or the engine from the vehicle, due to EGR and cooling changes. GM-51246 attaches to the left rear of the cylinder head, and allows a lifting chain to be attached. GM-50426 replaces GM-50421, which is used on 2010 through 2012 model year engines, and will clear obstacles in the area. GM-51246 includes hardware and a spacer to ensure it is mounted properly to the head.