The gallows went to Seven Acres Antique Village outside Union, IL. I remember seeing it on display there. It is now a western-themed park called Wild West Town (with a very good attached steakhouse BTW) and I don't know if they still have it or not.
I understand recent research (a book?) concluded that Terrible Tommy O'Connor successfully evaded capture, made his way back to Ireland and subsequently died in the Irish Civil War.