how can i tell a real ss

looking at buying a 1970 LS5 454 chevelle how can I tell if its a real SS I have the vin # and the information off the cowl tag. checked the numbers on the block and heads and they come back as a 1970 454 390hp mt LS5 can any one help with the car part of this.

Try here.

http://www.chevelles.com/shop/ss_ident.html

Try here.

http://www.chevelles.com/shop/ss_ident.html

Here is another place to check VIN's for what the car really is.
http://www.gaspumpclassics.com/resources/vin_decoders/chevrolet_vin_information.cfm

There is no way to tell if a car is a true SS by looking at the VIN # after 1968. All SS models up to and including 1968 started with 138.
69 and newer you need to look at a build sheet. That's why the 69 and newer models are so easy to clone.