Dual tires on rear axle????

Mine in the pic below is a 78 Dodge and only has singles. I was wondering the same thing myself. The GAWR for the rear axle is 5360 lbs. and load range E tires I believe are rated for slightly over 3000 lbs.
Seems to me to be cutting it pretty close when fully loaded...

On my former 1978 Lindy built on a Dodge Sportsman chassis there was a sticker on the backside of the closet door that described the drive train details. Might look for something similar. Showed tire pressure, tank capacities etc.

Hope this helps.

You can try a search on the internet for spec. It was not uncommon for the Mini series to be single rears on those under 20' in length back in the early 70s. There should be an Id sticker on the drivers side door area or glove boxes with weight and tire information.

Where can I find what mine was equipped with?

Some were made with duals and others only had singles. It depends on the size and weight of the class C.