It's undoubtedly doable, just make sure you have a good enough driver and/or car. Around 6000 points should give you a good starting point.
Take a Ford GT or a Pagani Zonda (or any other eligible supercar) and tune it to around 600-700 bhp. Buy upgraded suspension if you like, replacing the gearbox isn't necessary. Lighten the car if you want to. The tuning isn't so important as the B-Spec Botcher runs well on default settings. Put on hard or medium Sports Tyres (depending on the track) and set the pace on 3, overtake. Lower the pace if the driver seems to be having trouble, he'll take back on the straights what he loses in the corners.
This is what I would do, I'm not sure if it works but the opponents should be crushed quite easily.