I've just got my copy of "In car 956", a DVD from Duke that's basically loads of in-car footage from various tracks with Derek Bell driving a Porsche 956 in 1983. What an amazing DVD! There's a 6:41 lap of the 'ring on there, which is the 5th fastest time ever! It's mad, he's doing 195mph on the downhill section half way round. There's a couple of laps round Le Mans as well, before they put the chicanes in the Mulsanne straight. The Porsches were hitting 246mph down there apparently, certainly looks fast! If you have any interest in motorsport at all you have to see it.
I've got another DVD with a few laps on, the Skyline one, also from Duke. It's one of the original development drivers who's done 10000 laps round there going round in a seriously modded Skyline on a public day.