Searching for information on the Dillon Family

I am looking for information on Daniel Dillon (1813-1890) and his wife, Catherine Mahoney (1817-1882).  From their gravestone, it says that they were from Bulgadeen, County Limerick.  Other family information leads us to Bruff and Grange.  I am unsure of when they immigrated to the United States, but they lived in Newport, Rhode Island.  They had 4 children, John, Nicolas, Johanna and Daniel P.  John and Nicolas were born in Ireland.  Johanna and Daniel P were born in Newport.  That puts there immigration between 1853 and 1855.  Any information on parents, siblings, wedding information, etc. would be greatly appreciated.