Post #4 led me to go back to the very 1st picture and blow it up to see more detail. It does look like a dyno and the fellow with the lever uses it to put a load on the vehicle. Whatever is going on has drawn a small crowd of observers. Counting the hat brims at the very edge of the picture, I count 9 or 10 guys watching.
I got it large enough to fill half of a standard sheet of paper and when I printed it, it came out a lot lighter than the original thumbnail. I can clearly see the facial features of the guy in the driver's seat and can count the rafters in the roof structure. Below the spare tire is a rod apparently hooked to the rear axle to hold the car in place. What else do you see? Has anybody ever seen anything like this before?