Jim, very cool photo. It very well could be Green Hill Speedway, but there's just not enough landmarksto say for sure.
My gut instinct is that it isn't Green Hill. In the article about the opening it discribes steps cut into the dirt hill with cinder blocks set out for people to sit on, and you can kind of seethose stepsin the poor quality newspaper photo of Green Hill I posted. Also, Green Hill was opened in 1955. I think your photo is much earlier. It became the thing to do to cut out the back window around 1951-52. The car in your photo doesn't have that and looks typical of the cars prior to that modification. Then again, not everyone cut their window out.And the writing on the rear quarter panel looks typical to the late 40's - early 50's writing of who owned and built the car.
It appears the car number is actually 7 with an added 1painted on for this race which would indicate the car is from out of the area or out of state and another car from the area got the #7. The only #7 from the early days in the southeast with the stylishlooking font like that that I can think of off the top of my head is Johnny Roberts from Baltimore, Maryland.
Where did you find this photo?