Hi-speed strobe dilemma..

In an industrial project, I am confronted with an issue of having to employ shutter speeds above 1/500 (preferably 1/1000 or higher) and use a strobe for fill flash. Since the subject distance is about 50m and the subjects are moving type (vehicles on highway, they need to be pictured as sharp as possible) I am planning to buy a powerful strobe of at least GN70 at ISO 100. The cameras to be used are the D300S and D800E; the angle of view is about 35-40 degress (not so wide.)

My inquiry: Is it possible to employ Strobes at these shutter speeds? Both of our cameras have Auto FP Hi-speed sync. however I have no experience with any shutter speed above the sync.one, that is 1/250s. Also what features should I look for while buying a strobe? (For example I think those having shorter flash durations than 1/1500s could be better choices).

Thanking you in advance for the insightful commentaries and recommendations.

Regards,

Bob

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BobYIL