Great photo. How things have changed - the road is now a 2-lane highway each way, as a main feeder route to Belfast. The near end of the pits is now a Toyota dealership, and the grandstand is now a second-hand car dealer/car wash. The road must have been straightened when the new road was constructed, as it barely curves at that point. A very large local authority housing estate now takes up the fields in the distance.
A memorial plaque has been placed beside the road to indicate where the pits once stood, and originally it was accompanied by a replica pit, but local disaffected youth decided to burn it down one night. I attach a photo showing the area as close as I could find - this shows the road in the opposite direction, the pits stood where you can see a small lay-by and what seems to be a bus stop sign, on the left hand side of the image.
BTW the 2 Ford Model-A tourers were entered by Wrights of Belfast, local Ford dealers who presumably did so for the public exposure rather than any competitive intent.