Looking for Shea OR O Shea from County Cork Ireland

My father's family arrived in the US during the potato famine and settled in Nova Scotia, then family members settled near Detroit MI.
They are called Shea, but it has been suggested that the name may have been O'Shea until they arrived in Ellis Island.

My grandfather was Robert Shea, his father may have been Thjaddeus Shea or a similar first name.

Any information on the family would be appreciated.\\Respectfully,
Kelly