I came across these awesome behind the scenes shots on a pbase gallery of a person named Richard Guillis. All three were taken during the filming of the opening scene. Unfortunately, now all that's left on his site is one small gallery with no more TLB photos.
Here's the '55 Chevy with alot of "LA Street Racers Assoc." denim jackets wandering around.
This one features what looks like the 1970 AAR 340 6-BBL 'Cuda which races the '55 Chevy in the opening scene (and which Taylor later says was a 'Hemi' in the next scene). That also looks like that might be director Monte Hellman (with the wild hair) leaning against the car.
This one looks like they might be getting ready for the "scatter" scene.