don't need a 4wd. just make sure you have good tires and a real spare. road is totally driveable in 2wd. it's just super washboard and the chert near uhebehe crater will puncher your tires if you drive fast.
I don't live in that area, I only visit 1-2 times a year via rental car from Las Vegas. I took one to the Darwin waterfalls one time and that was a rough road for 5 miles... I don't think I'd risk the longer journey to that Racetrack in it unless it was a different kind of vehicle.