A Region 1 DVD documentary on the film, "The Making Of Grand Prix", was released last year. I haven't seen it, but I've read that it's horrible - a 20 minute compilation of promos from the '60s that apparently doesn't have much footage from the actual film. It's nothing that John Frankenheimer would have approved for DVD (or its release in the '60s).
There's a rumor that Grand Prix has been mastered for DVD but the release has been suspended due to legal problems. Just a rumor, though. Frankenheimer has passed away, but hopefully some kind of special edition set can be put together. A commentary track with James Garner, the film technicians, and the drivers from that era would be worth hearing...
I'm a member of a Frankenheimer discussion group at google.com (my user name there is budziat). It's only a year old, and we need new members to get some dialogue happening.
http://movies.groups.yahoo.com/group/frankenheimer/
A new special edition DVD of "The Manchurian Candidate" is being released this summer, and the Jonathan Demme re-make is coming out this Fall (?). Hopefully this will lead the studios to release some more of Frankenheimer's films on DVD. Grand Prix is the main MIA at this point...