That's the body buck tag. It won't give you the rear end ratio. For that, you'll have to look on the tag on the driver's side door (inside the door jamb). Look under the "Axle" heading on the tag.
Assuming the door hasn't been replaced, that code should reference you to what ratio you have.
Here is a link that may help you to cross-reference the codes:
http://www.ultrastang.com/Rearinfo.asp?Page_ID=5