Olson Emmigration

I am trying to find an emmigration record for my ggrandparents, Gunhild and Sivert Olson. They both supposedly left Norway around 1871-3. His parents managed Melhus farm, Sor-Trondelag, and he was born 7 Dec 1844. She claimed birth in Telemark, 2 Juli 1853 but I have not located family in records. Her mother came to USA about 1890 and gave her name as Inga Johnson. As you can see, I'm not sure of Gunhild's surname. I think they may have gone through Canada as my grandmother claims birth in Thunderbay, Ont.