Here's what one of the old timers who has owned a number of mopars ever since he bought (one of which is a 65 Cuda) said about some differences in cars he's seen that came out of the Canadian plant:
"In 1956 the Plant produced a Plymouth with a 303 cube and it took the stock production car speed record at around 126 mph. Only the Plymouth's produced in Canada had that engine. There also was some difference in some of the flat head 6 cyl produced in the late 40 s,but don't remember just what the differences were. Watch for those forums as they all think that they are experts.
Just remembered about the 66 Charger that had a factory 318 c i in it and was told that it came from Canada also.The 318 was not supposed to be in it according to some but I saw one."