Not sure of your source for 1740 but Bill MacAfee's database lists more-
Kilcronaghan- Henry McKee
Maghera- Will. McKee, Wm. McKee
Magherafelt- Henry (McKees), John, James, Wid.
In 1766 John and Matthew are in Magherafelt as well as the John in Desertmartin (not 2 Johns and a Matthew in Desertmartin.
https://www.billmacafee.com/18centurydatabases.htm