Hi Joel

Have you tried to find him arriving Canada ? A lot of English/Manx/Scots went to Canada first then crossed the border.
Found the family in 1860 , South Salem, Marion, Oregon , and included W Clark aged 27, a male born IOM , this no doubt is James' brother William , christened Jan 4 , 1834 Ramsey.
Manx Note Book shows William still in Oregon on 1880 census.
I.G.I shows James buried 1879 Salem Pioneer Cemetery.
On Living Places , there is a story on the Clarks, Early Settlers in East Salem , historic district of Court and Chemeketa Sts.
The U.S. National Archives seems to hold Immigration Records on Film in this period , they state the records are also available in certain libraries, have you tried this source ?
Cheers
David Dwyer