McDill, McBride, Gahey(or McGahey), and Dunlap - searching for birth parish in County Down

Searching for the birth parish for the following family line, all of whom were born in County Down, so I would think the parishes in question would be the same or very close to one another.

Samuel McDill, b. 10 January 1745, County Down; d. 9 May 1811, Guilford County, North Carolina

married...

Janet Elizabeth McBride, b. 3 November 1748, County Down; d. 18 July 1838, South Carolina

who was the daughter of...

Jean Gahey or McGahey, b. 1722, Ireland; d. March 1794, Ireland

and...

John McBride, b. 1721, County Down; d. 20 January 1806, Guilford County, North Carolina

who was the son of...

James McBride, b. abt 1700, County Down; d. ?, supposedly County Down

and ...

Elizabeth Dunlap, unknown birth and death dates/places (assuming Ireland) 

Thanks so much!
Laura