Hi Andrew. Just came across your posting. I am also looking for Irish GORE's who have a family lore of the connection to the Earl's of Arran. I suggest you check out BURKE's PEERAGE which would be at you largest local library for the Earl's of Arran, and other related Gore lines. I do have copies, but don't have them to hand at the moment. Will look at them in next couple of days and get back to you if I see anything of interest. Have you tried just a general internet search with his name or 'Gore' and 'Artarmon' as search keywords.
Just out of interest - where did your Gore die? In NSW? or did he return to Ireland?