Oh Yeah, I was working on Grand Prix as that time seems by far impossible, but TG people seem to think it can even be beaten, but won't say how.
Anyway, the current release build of BizHawk runs constant length frames for A2600. In other words, all frames are 262 scanlines long. This causes some adverse side effects for some A2600 games because start up times can vary and put frame boundaries in the middle of video frames. Also some frames in games are 263 scanlines long, so this causes a cycling effect.
By pure coincidence, I was working on another bug and realized that it could be solved by only changing frames on video frames, so this is the current implementation in the dev build. So, in that build, frames change at the falling edge of VSYNC.
Side Note: A2600 core originally changed frames on video frames and at some point was changed to constant length frames. And now I changed it back, we aren't very consistent!
Here is a movie that gives a 32.74 in the Dev Build. I'm not sure a 32.74 is possible in the release build.