Most Saturday nights my uncle who worked for a Ford dealership would take me and my cousins to Riverside Speedway in Agawam,Mass. I too can still smell and hear them as they were great to watch as a kid.
I’m almost certain the “contraption” on back is an air compressor. Although I’m not old enough to say from experience, the tracked vehicle was most likely used to move heavy bombers around on an unpaved air base during WWII.