Given that the actual size of each car will depend on the size of poster you get. I usually offer these in three sizes - 24,30,34 inches on the small side. In this case the smaller side will be width. The length will just be a ratio of what the width is. If we just plug the last hole in the lower left then the sizes would be 24x32.4, 30x40.5, 34x45.9 (special order for 36x48.5) So with 4 cars across the top and given a 24 inch width each car image will be 6 inches wide. If there were 5 rows across the top and a 34 inch version was used, then each car would occupy 6.8 inches. So depends on size as to how much car you get.
A lot have send images of their cars that are good enough to possibly go 24x32 by themselves. For those who did send in good images - if you order a poster, please ask if you would like one of these made for your car. The courier will not change one iota. Or if you have a super high resolution image of your car and want up to a 36 inch on the small side - let me know.
Anyway I digress. We shall take one more and call it? Vinb has sent a couple of cars he had back in the day, and if someone doesn't step up, I'll use one of his sweet racers.