Several years ago I did the Petty thing at Texas Motor Speedway. My fastest lap was 151, but I would have been comfortable boosting that by a few mph if the instructor had allowed it. The cars are very easy to drive.
I drove the same track in my Valiant convertible and was more nervous at 85-90, as the high-miles slant was wound out tight and 9" brakes don't give much confidence at that speed.