I have a 68 mustang with, what I think, is an extremely high ratio rearend. It really bogs down the 347 stroker that we just had built. The serial numbers on the differential tag are: CZ-F1 and 008a8931. Anyone out there know what these codes mean or is there a website where I can decode these no.'s. All the decoders I've found online are for the VIN. Thanks for any help.