Jody, awesome looking car. Sadly the trim tag info. and VIN will NOT tell you what engine it came from the factory with. All the SS labels, the 396 engine, the black tail panel, all could be added to enhance value or speed. Check the rear frame rail behind the drivers side rear wheel at about 1 o'clock and see if there is a apox. 3x5 inch steel plate welded to the frame with 2 holes in it, for hanging dual exhaust. If its there, the car did come with factory dual exhaust. If its not there, its not a SS396.
Also count your hood spring coils. How many fuel lines coming up to the fuel pump?
Get ALL numbers off the block and post them in here,that will also help the folks to help you figure out what you have.