Since every race is set at a PP limit (and only a few have more stringent requirements, such as "Normal Car" or from a specific country), as long as the AMG meets the PP limit you can use it in any race. (Note the initial PP is 584; that'll get you into the majority of races, if the PP is less (say, 550) you can mess with the ballast and Power settings (i.e. reduce the percentage from 100%) to get it to the 550 threshold, this actually is a good tip for ANY race where you have a car that is over by 1-40 PP).