Mary,
Thank you for searching those records.
At the moment, I am inclined to believe that the John Gill, Protestant who is one the list of Hydrabad convicts was one and the same man as John McGillicuddy, Catholic, in Darlinghurst Goal. I know it sounds like a stretch but the goal records state 4 separate times that he was on board that voyage.
I will keep an open mind and keep searching.
Thank you again,
Kevin McGill(icuddy)