I found the axle codes in the 63 Assembly manual. There is a stamped code on the rear cover edge, passenger side, at the 3 o’clock position. Mine is C-201. The C means 3.36, the 201 is the Julian date code (day number of the year). The only other codes are A for 3.08, B for 3.23. Posi rears would have a X in a circle before the codes. Hope this helps.