You have a dilemma and you'll probably need some additional piece of information about your biological father in order to resolve it. On the one hand, the George L. Harris, born in Georgia and living in Detroit in the 1930 census makes a good match agewise and locationwise to your mother to be your biological father on the otherhand, there is a black Harris family in Emmet County (Walter and Ida) in the 1920 census with young children approximately the correct age. In the 1930 census, something has happened to that Emmet County Harris family (possibly the father has died and the children are in foster care). At least one of those children (Walter) appears to be in foster care living with the sheriff and listed as white. There is also an Alice Harris b. 1924 MI, listed as a boarder in Emmet and possibly another child of Walter and Ida. George could have simply been missed in the 1930 census.

Have you tried getting the marriage or divorce records for your parents ?