If I might submit an idea from Ireland (featuring both parts thereof): how about, former Macfin Junction near Coleraine -- Magherafelt -- Cookstown -- Dungannon -- Omagh -- Enniskillen -- Manorhamilton -- Collooney -- Swinford -- Claremorris? I make this to be roughly 180 - 190 miles.
You can then add Claremorris - tuam - athenry, meaning you go. former Macfin Junction -- Magherafelt -- Cookstown -- Dungannon -- Omagh -- Enniskillen -- Manorhamilton -- Collooney -- Swinford -- Claremorris -- tuam -- athenry. I think Claremorris athenry is 73 miles, so your journey would be about 253/263 miles?
Oh, dear, I'm not in touch with things -- to my shame, I'd been imagining Claremorris -- Athenry still in use for freight. A quick bit of Googling, put paid to that notion. (Though I learn that track is still down on that section, under basic minimum maintenance.)