It looks a lot more like a 4.8 L Gen. III small block truck engine (Vortec 4800), or a 5.3 L (Vortec 5300). They're also St. Catharines products (so Steve would have ample opportunity to pose with one).
If you really want to be sure, take a look at the tall plastic intake manifold—that was always what stood out for me when I was at GM St. Catharines. Also note that the Corvette engines typically have the red-and-black covers, while the CTS-V has the silly-looking Cadillac engine cover. The truck engines are usually unadorned, like this one, though since it's missing its accessory drive (alternator, belts, etc.), I suppose that it could be waiting to be embellished further. (Though this looks suspiciously like the one sitting beside the line in the block assembly area, near the production/quality whiteboards.)
Check
here for more information and pictures, if you want to prove me right or wrong.