There is a lot of Busby information on Google and it might be worth also working on the Dunning connection. I think I have seen both names listed on Google in a contemporary reference and a family member might have an old family bible with hand written notes. A current family member might have done extensive genealogical research. If you were a member of the North of Ireland Family History Society they would print details of your search. The magazine they publish is widely circulated throughout the world.