Vital and Census records show many inconsistencies with the name McCullough. Everything from McCuller, McCullers, McCollough to McCullar has been recorded. Obviously, McCullar or McCuller is a 'southern' version due to the pronunciation. Some of these records were correct and legal as names change over time, while others were not.
Here is proof that the McCullar name is for real and not just a written mistake.
This comes from Ernie McCullough, in an email to me:
"The story goes that when Cuba Mae Doak married into the family [to Charles Henry McCullough], being a school teacher from Tennessee, she convinced the family that McCullar was not the proper way to spell the name, that it should be McCullough. All of Perry's children then changed the spelling to McCullough except for James Randall, who decided to keep the McCullar spelling. So all of his children spell their name McCullar."