I would just add to this, that I am also descended from a "McCullagh" family of Armagh, who emigrated to Australia in 1863. An Alexander McCullagh, wife Anna (nee Munro), and five children under 10!
They came from "Denihora" or "Derrahorra" (somewhat illegible), which I am told is now part of Mullaghbrack Parish, Markethill.
They were also buried in protestant cemeteries in Australia, e.g. CofE.
In the Queensland immigration shipping records, they are listed as McCulloch.
Fiona, Brisbane.