yep, small world indeed.
The auxillary springs were used for supporting heavy loads. They would only really help when the truck was loaded to its max. capacity. There's a leaf like spring that connected from the frame to the axle (I believe). When the load hit its max. capacity - the spring would help support. It did add like 500lbs more capacity to the GVW Range though, for each side - so a 1 ton truck would be a 2 ton?? Not sure the specs - someone else can correct me.
It sounds like a good match for that frame, if its intended use was for Ambulances, etc...
You can see the auxillary spring mount in a pic in my build post.
Someone took the springs off mine though, prob. rusted away.
See the bar bending downward going near the tire:
Maybe the truck was a left over from a dealer in town, who didn't sell it or something. Or whoever bought it - didn't convert it to whatever.
Or maybe they stripped it down, took whatever was on it off the back.