Thanks. I know that by about 1863, my great-grandfather John was using "McIver" as the spelling. I have been told that he was made to change the spelling -- probably when he enlisted in the British Army that year -- but so far I believe the change was from "McIvor" to "McIver." The only really solid information I have is that he's from Tyrone (he reported this in the 1911 English census) and that his father was named John McIver (which, incidentally, is how it's spelled on his marriage registration). There was a family of McIvors in Termonmaguirk parish that I am currently focusing on, but I have never found a smoking gun to prove the relationship.