This car is called a Schnable car. I photographed it in Suffern NY around 1987. This car would hydraulically lift the load (usually a transformer) on and off of a truck eliminating the need for a crane. The caboose came along with it.
Many Schnabels are still in use in this country. They are certainly fascinating cars to both see and model. I have been looking for plans to build the one in the picture but have not found good data. I have built a couple in N, the accompanying photo being one of them.
Very cool! Great site, the car I photographed is on there. As far as modeling, looks to me like you didn't need any plans. I saw one of these cars in HO brass back in the early 1980's.
You can get by making your own drawings as I did with my first effort but, some critical measurements help in the construction. I've never minded "it looks right" but, you know, there are some rivet counters out there!