Typically the two studs on the valve cover indicate either a 216 or 235 splash engine. Some later engines are dolled up to look like the earlier 216s by doing that. The 216 will have a side cover that extends all the way up and through the spark plug holes until it hits the valve cover. Some of the 49-53 trucks had splash 235s that had the shorter covers used on the later engines (thanks Tim!).
From my understanding, you can feel the difference when stepping up to the 261, but I dont have that experience.
I dont know about canadian casting numbers, but hopefully that helps to sort out the mess.
Jeff
