I am reasonably sure of the birth year. My first information came from a letter written by my great uncle who gave the year 1776 in Virginia and the name of his wife, Nancy Lawson. He also gave the information that he had a son Pleasant b. 1804 who married Margaret Bledseau (as he spelled it) b. 1803. They had a son James b. 1825 who married Mary Parson b. 1832. James and Mary were married in Lawrence County, Ohio in 1848 and had a son Pleasant b. 1849.
This is all confirmed by the 1850 census for Lawrence County, Ohio, which lists all of these names with the appropriate ages, including William who was 75 in 1850. The census lists them with the spelling Bolan, but these are clearly the same folks that are on the Lee County Virginia tax lists around 1800 and then the Hawkins County, TN tax lists in the 1830's. See: http://www.lawrencecountyohio.com/census/1850/Mason.htm
William Boling's (Bowling or Bolan) other children were Enoch b. 1808, Thomas b. 1812 or 1815, Riley b. 1816, Winnie b. 1818, Mahala b. 1826 and Laura b. ?
According to the 1850 census, William age 75 and Nancy age 70 are living with their son Thomas and daughter Mahala, and are neighbors to son Pleasant and grandson James and their families. There were in Tennessee as late as 1840 when grandson Carlos was born and moved to Ohio by 1849 when great grandson Pleasant was born. Pleasant born in 1849 was my great grandfather.
I hope this helps.