I watched THX 1138 for the first time yesterday, and for anyone whos has wached it, the cars in it a SWEET! took me 45 min to figure out what kind of car it is.... a 1960's LOLA T70 MKIII. I must own one someday! BTW the movie is great! watch it!
IIRC George Lucas' budget for
THX 1138 did not have room for contemporary race cars. Instead they used clones (VW pans with a body made by Fiber Fab, a Santa Clara California company that made GT40 clones and a Myer's Manx rip off).
I am currently in the process of reading Mark Donohue's book
The Unfair Advantage which is a great history of US Sports Car Racing and the early days of the Rodger Penske racing team in the 1960's and early 1970's. In the book he talks extensively about the Lola cars like those pictured.
If you want to see real race cars on a real race track in a movie, rent Steve McQueen's
Le Mans. It does not have much of a story but it is worth renting for the driver's point of view shot in a Porsche 917 going about 180 mph
in the rain.Scott