Hy Bill Hanlon, Canadian light GMC trucks of that era are powered by Chevrolet six cylinder engines, I assume the "C" in front of the numbers designates Chevrolet, but I have no evidence to confirm that. The heavier trucks that actually have GMC engines do not use the same system as their American cousins, rather than use the cubic inch displacement as the first three numbers of the engine serial number they use two letters, the 248s use a "G" and another letter at the front of the engine serial number, hope that helps.
