HALVERSON? JOHNSON? Bergen/Stavanger

Looking for information on either of my grandparents. Halver Halverson b: 1878 Died in Iowa, USA in 1959 Halver is said to of come to America with his parents around 1880/1881? He was born in the Bergen area, and I believe his parents names to be Halver & Abigail. Looking for departure port/ship, any information!!! Belle Johnson (halver's wife) b: 1877 died: 1946 in Iowa, USA was born in the Stavanger area, and family history says she came to America around 1902/1903 as a pregnant widow. (If that is so, I don't understand the use of her maiden name...but who knows what real story is...her husband/lover/intended was said to of been lost/killed at sea) It is also said that she traveled with her brother, Ole Johnson....she married my Great Grandfather (where? when?) and settled in Iowa. She had more children. I'm looking for any additional information someone could provide about either families emigration, connections to relatives still in Norway, etc....thanks so much! Stacey