Which races are you referring to? I don't have the impression any of them are particularly tough.
The answer also depends on whether fuel consumption and tire wear are on. Or bop in missions.
Generally, the GT300 BRZ gr3 with medium turbo can win just about anything. Silvia Aero gr4 same. Both are easy cars to drive.
If I remember correctly I used Nissan GT-R GT3 '13 for Spa and Suzuka, VW Beetle Gr.3 for Lago Maggiore (Italy), Mazda Atenza Gr.4 for High Speed Ring and detuned Nissan GT-R '17 (600PP) for Tokyo Expressway.
If you want it easy on the 800 pp races, take a gr2 car, the Nissan GTR '08 is a fast and forgiving car for example.
The 730 pp Gr3 races, I don't remember, but I guess the Mazda RX Vision should probably do well.
High Speed Ring 630 don't remember either. Would give the gr4 Supra or Gtr a try: relatively fast cars.
Tokyo 600 is a tough race. There is an entire thread on this site on this race. I won this one recently with the NSX '17 on SM tires. Do 7 laps first stint cause the tires wear more later on the dry circuit. Odd ball choice here: 1965 Honda F1 car. Does entire race non stop on SS tires and good fun.
GL HF.
