Not sure what you mean by "the ownership says it is a 322". The stamped number pretty well confirms that the engine is original to the car, and it seems highly unlikely that GM would make a mistake as extreme as installing a "wrong" engine at the factory.
The block casting number would be the best way to identify the engine for certain, as the 3/8" bore difference precludes using the same casting for both engines. I have no good reason to assume that Canadian casting numbers are the same as US, but it couldn't hurt to see if your number shows up on this list.
http://www.buicks.net/shop/reference...g_numbers.html
Ray
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