I looked on www.irishgenealogy.ie which has Dublin city church records (RC and C of I). The best record I could find was a John William Downe in 1839.
Area - DUBLIN (COI) , Parish/Church/Congregation - ST. CATHERINE
Baptism of JOHN WILLIAM DOWNE of 70 MARROWBONE LANE on 19 May 1839
NameJOHN WILLIAM DOWNEDate of Birth6 April 1839Address70 MARROWBONE LANEFatherWILLIAM DOWNEMotherELIZA DOWNE