Canada's national missing person database is neither user-friendly nor searchable, so I'm going through open cases one by one to see if there are any matching cases that the WebSleuths community think are worth calling in to the Tofield police - I'm new to this "web detective" thing.
Another case that I think might be a possibility is that of Rene Joseph Bruneau.
Rene was born in Saskatchewan in 1941, which would make him 35-36 at the time of the murder - exactly the age range that the Coroner predicted. His missing persons file lists him as "white", but he is also noted to have a dark complexion, black hair and brown eyes. Thanks to a quirk of Canadian law, many white/Native mixed race people were classified as "white" under the Indian act from 1867 - 1985, and since he's from North Battleford, an area that has always had a large First Nations and Metis population, it is not at all unlikely that he was actually mixed-race. The fact that he has a French surname in a non-French area also points to the possibility of being mixed-race/Metis. Burneau disappeared from a hospital in Saskatchewan in June of 1965. He was apparently there the previous day, but was gone when staff did morning rounds the following morning. It doesn't seem impossible that he may have made his way out to Alberta from there. He reportedly had a scar across his forehead from a surgery to remove a tumor - could a healed scar be the "childhood illness" that the coroner was talking about? He stood 5'7 and weighed 154lbs, putting him squarely in the height/weight range for Sam.
There aren't any better pictures available, unfortunately, but based on the one we've got, it looks like Rene might be a rough match for Sam's face shape/jaw.
The Doe Network: Case File 4292DMSK