O'Mara or Mara

Hello, I'm looking for info on my great grandfather, Dennis (Dionysius) O'Mara (Mara).

I believe he was a tenant farmer in the area of Clonmel/Kilsheelan since my grandfather's (Michael) records indicate that he was born in Kilsheelan area on May 5, 1862. 

The only thing I have is a date of marriage of April 24, 1850.  His wife is given in family records as Margaret Kennedy however his son's (my grandfather) death certificate indicates Dennis' wife as Margaret Keating. 

I'm not really sure where to go next.

I am poking through some of the online church records for St. Mary's and Gambonfield parishes but it's pretty tedious.

Michael O'Mara came to Canada around 1883-5 and died in Chatham Ontario in 1933.  As far as we know he was the only child of Dennis O'Mara and Margaret Kennedy/Keating.

Thanks,

Jerry O'Mara                                                                                                                                                                                   Oshawa Ontario, Canada