That's right, the historic race in A-spec is giving a lot of people problems. I hear there are two good solutions.
1. If you are an excellent driver, fully mod out the countach and you stand a strong chance. To make it easier on yourself, keep restarting until the 2J or Toyota 7 do not appear at the front of the grid.
2. The '69 Camaro (premium) that can be purchased at the dealership can be modified into a race car. Apparently, people with average skill can pretty easily beat the competition with this car fully modded.
Both of these options are much cheaper than purchasing a historic race car.