The codes are on a white sticker that is usually on the bottom of the console lid or on the back of the spare tire cover. Yours might be in a different location. If you can find it you will have all of the information about what your car came with, including the engine, transmission, suspension, brakes and other options. The codes are in alphabetical order and the rear end codes start with a G, the engine codes start with a L and the transmission codes start with a M.
Tom's Differentials is a great place to get Eaton parts, installation kits and AAM axles. His prices are good and his parts are among the best. He is kind of a grumpy old fella, so don't take it personal if he isn't cheerful.