Your Dad...
https://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=105611407
"Georgia World War II Draft Registration Cards, 1940-1945," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q2QZ-TD7X : accessed 26 June 2017), William Louis Monk, 1940-1942; citing Valdosta, Lowndes, Georgia, United States, Records of the Selective Service System, 1926 - 1975, RG 147, National Archives at St. Louis, Missouri.
Possibly your Dad:
"United States Census, 1940," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:K7GG-BFG : accessed 26 June 2017), William M Monk in household of Selina Monk, Militia District 661, Lowndes, Georgia, United States; citing enumeration district (ED) 92-2, sheet 9B, line 59, family 166, Sixteenth Census of the United States, 1940, NARA digital publication T627. Records of the Bureau of the Census, 1790 - 2007, RG 29. Washington, D.C.: National Archives and Records Administration, 2012, roll 691.
If this is your Dad, the mother's name was all wrong:
"United States Census, 1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MJ6J-DPN : accessed 26 June 2017), William Monk in household of William B Monk, Naylor, Lowndes, Georgia, United States; citing ED 117, sheet 13A, line 37, family 57, NARA microfilm publication T625 (Washington D.C.: National Archives and Records Administration, 1992), roll 267; FHL microfilm 1,820,267.
"Georgia Death Index, 1933-1998," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:V492-KKX : 24 December 2014), William L Monk, 06 Dec 1977; from "Georgia Deaths, 1919-98," database, Ancestry (http://www.ancestry.com : 2001); citing Lowndes, Georgia, certificate number 038329, Georgia Health Department, Office of Vital Records, Atlanta.
"United States Social Security Death Index," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:J2FN-Q29 : 19 May 2014), William Monk, Dec 1977; citing U.S. Social Security Administration, Death Master File, database (Alexandria, Virginia: National Technical Information Service, ongoing).