Looking for GG Anton Olson from Norway

Hello All, I am looking for Anton Olson/Olsen/Oleson, my gr. grandfather, b. between 1845 and 1850. I'm told was born in Tronheim, Norway. He immigrated to America sometime before 1870. He married in abt 1871 to Anne Kristina Guldbransdatter in Perry, Dane Co., WI. Anton and Anna had 6 children that I know of (surname Olson) Ole Gunerius, Anna, Karl Marcus, Myrtle and Andrew. Andrew was my grandfather b. in 1878 in Chippewa Co., MN. I don't know where the other children were born, except that their first child, Ole, was born in Perry, WI. I have searched everywhere I know to find this family without success, so I am hoping that someone here might be able to help me. Thank you. Myrna