Torgrimstuen

My great great grandfather Arnon 'amon' Peterson was born in Fluberg, Oppland Norway in 1866. He married a woman named Johanna. I don't believe his last name was always Peterson. I believe it was changed when he emigrated to the US. My grandfather told me our last name used to be Torgrimstruen, which is the name of a farm in fluberg. Can anyone help me find a birth record or marriage record for arnon peterson or his family. thanks