I recently purchased a 1970 Mustang fastback. It has been modified and I am trying to figure out what I have. The first item is the rear end. The tag reads "WDZ-81 9EB 3L00 8 875A". The "1" after the first "8" might be an "I". I am almost sure that it is not original to the car because the gear ratio does not match the data plate and the vent tube is on the passenger side of the axle. Can anybody help? Thanks.