This is a project I started today. A company called Fesco made a toy box caboose around 1973 for $17 at the time. I recently acquired one through eBay. I had no plans to work from so I improvised my own design along the way. The frame consists of a one by two steel tube with short pieces used in additon for side bearings. The floor is two layers of 3/4" plywood screwed and laminated together with construction adhesive. The carbody is screw and glued to the top layer of plywood. The bottom layer of plywood is concealed by a piece of one inch channel screwed and glued to each side as well as the pilot on each end of the caboose. The trucks and couplers were acquired a few years ago through different suppliers on eBay. The trucks are manufactured by K and M and are Aluminum. The couplers are RMI and made of stainless steel. I plan to order grab irons from Precision Steel Car Co.. I am still brainstorming on what to do with the end handrails. The smoke stack will be 1/2" iron pipe with a tee. I have enough plyoow left over to make a seat so Karsen can ride in it or perhaps a seat and cushion at the roof level with some foot pegs for an adult.