"In Car 956" was one of the first videos I ever bought (it took me a long time to get round to a VCR!). As to Le Mans vids, I have all the Sportseen "RLM" commentary tapes and they are all excellent, but 1990 is the best for me, closely followed by '88. Most of them are still available from Duke, as is "In Car 956" (as AAReagles rightly said).
The added-on commentary tapes which we have been subjected to since 1997 have been very disappointing - great footage (although they always seem to manage to miss the major shunts!) but the RLM commentaries were
so good!!