Rusty O Toole gave a good rundown on why Canadian Pontiacs after 1955 have Chevy powertrains. It's not just the powertrain - the entire chassis & much of the inner sheetmetal is Chevrolet on 55 & up cars. Basically, GM of Canada stamped unique outer body panels - they look like American Pontiacs, but scaled down as required to fit the shorter Chevy platform. Thing is, they did such a good job of making the Canadian panels look like American ones that some people don't realize there's a difference. It becomes a problem when you can't figure out why the rust free Catilina fenders you bought won't fit your Parisienne....sometimes you have to learn stuff the hard way...but I'm older and hopefully smarter now. There are some other pretty cool cars out there - the "Custom Sport" is the Canadian version of the 2+2, available with the same powertrains as an Impala SS, and they are really cool.