Pace--I found many marks on my '68 of different colors, and I've been told they don't mean anything because GM didn't use inspection marks until the '70s--that they were simply vendor markings. I found a yellow "L" on the RS frame under the A-frame at the shock hole, a long yellow scrawled mark on the LS underside of the frame forward of the A-frame, as well as lavender and orange markings on my spindles, ball joints, tie rod ends, and drag link. I also found "68" scrawled in yellow on a brake drum. They may not mean anything, but I'm duplicating them anyway. You only get one chance to put your car back the way it was.