nikon 70-300mm vr too slow??

[Franglais]

I'd disagree there, it depends on what subject you're panning with, from how far away, with what focal length, and what effect you want.
I can go down to 1/25, with care, and get a very different image from 1/250.

This is the guy who knows. My motorsport experience is limited.

That still means that the 70-300 is going to be suitable. I believe you have to turn the VR off if panning.