At the very minimum, it sounds like you are dealing with a seller that either doesn't know what they have (that's one problem) or is being deceptive (that's a bigger problem). I would use caution. The good news is that you might get a Z28 for the price of an SS so it could work to your advantage.
EDIT: BTW, did you check sites like this for the VIN decode?
http://www.chevy-camaro.com/chevy-ca...fourth-gen.asp