Floyd's of Cork or Donegal

I'm trying to track down where in Cork my home parish may be. I doubt anyone will have any ideas, but it is worth a try! My ancestors (4th great grandparents), married in 1787, Cork Ireland:

Robert L. Floyd Sr. BIRTH 1765 • Countynorthern, Cork, Ireland DEATH 1821 • Cork, Ireland (Had a brother by the name of John Floyd that migrated to Pennsylvania, USA. 

Sarah (Jane or Peggy) Campbell BIRTH 1769 • Cork, Ireland DEATH 15 MAR 1856 • White Mills, Hardin, Kentucky, USA

The two of them are as far back as I can trace. They had several children in Ireland as well, Mark Campbell Floyd, Sarah Jane Floyd, Robert L. Floyd Jr., Isabel Floyd etc.

Jane (Campbell) Floyd is represented in the manifest of the ship logs for a Ship sailing from the Port of Londonderry in Ireland under the command of "F. I. Luberg" on 23 June 1821. I have not located a marriage certificate or record of marriage/bond, etc. for Jane and Robert Floyd. Although many Online sources state that they were married about 1787 in County Donegal.