No because the thermostat opens before then. Once the thermostat opens, the entire system won't see more than 200 degrees or so depending on the rating of the thermostat plus about 10-20 degrees in soak temperature. Soak being after you turn the engine off, temperature rises a bit before it goes down.
So you say your Canadian GMC 920 (3/4 ton) came stock with a 261? Are you sure? I know they put the 261 in Canadian Pontiac cars, but always thought GMC had their own stream of engines.
