The William McGilvery in the book is of NH Men in Col. Henry Jackson's MA Reg.
There is a William Gillivray 1790 census Dutchess, NY 1790. Same Person?
The William McGillivray in 1790 Dutchess ,NY census would have to be born c.1758 or earlier, if he is is the father of Christina McGillivray b. 1778.