emigrant 1871from Toten township, Norw.

On May 1. 1869 a Matias Thorstensen Rustad left Kra. bound for La Crosse. Some years later; probably in '71 his wife Olina/Oline b.ab. 1829 and their daughter Tonette b. 1856 also crossed the Atlantic. (I can't find them at Digitalarkivet; but my sources says they left '71) I'm trying to follow their tracks; but I can't find Mathias or his family at Census 1880; Norw. living in the US, or in any other archives. (Olines patronymic was Evensdatter) I don't know what surname they used; Mathias probably "took" the Rustad name at the time he left Oppland County, Toten Township together with my Great-Grandfathers brother. (They wasn't related) How can I find them or their descendants?