Here he is in the Norwegian 1865-census: click here
Parents are Lars Haraldsen, born in Gjerpen approx. 1814-1815 (Gjerpen is just north of Porsgrunn in Telemark county), and Inger Johanne Aslaksdatter, born in Porsgrunn approx. 1815.
Here is a link to the "Skien Genealogical Page" You can find emigrants from Gjerpen and Skien there, but I'm not sure if people from Porsgrunn are listed. It's a good page though!
Are you talking about the Iver M. Larsen from Norway who worked for the U.S. Lighthouse Service at the keeper of the Supply Depot that was on Castle Pinckney and later moved to the Tradd Street base in Charleston? I have a little bit of information on him.