Steve, watch the video again, and you can see ol' Eldon is ACCELERATING down pit lane!! While the story about "no cones" and a "drum brake car" may be true, there was absolutely NO reason for a driver to continue accelerating a Pace Car down pit road after coming off the track! Indy has a looooong pit lane, and ol' Eldon should have been doing about 40 mph when he passed the start/finish line.
What's probably more believable is that ol' Eldon was excited, he was showing off in front of hundreds of thousands of people, he thought it would be cool to "run with the pack" for a couple seconds, and unfortunately he lost control. There may have been a "misplaced braking cone", but when you've supposedly rehearsed this a dozen times, you'd have to realize something was
seriously wrong as you pass the start/finish line bricks at 100 mph!
I think a better story is that because of Mopar's horrible 1971 build quality, the throttle stuck wide open, Eldon slammed on the brakes, the rear end hopped violently, and he lost control.