This page describes how I converted this car from the toy-train couplers and wheels to the scale ones. The S Scale America box comes complete with the scale wheels, but you will have to buy the scale couplers separately. Since the Proto Max couplers are my fleet standard, I installed those. The tools required for this project are a set of small, jewelers screwdrivers, tweezers, drill and tap for the coupler screw, and perhaps a pair of magnifying visors. The first photo shows one of the trucks on the car as it comes out of the box. It has the large American Flyer-compatible couplers and wheels with large flanges.
The trucks are connected via a single screw and are easily removed. The underbody has a hole and two protrusions, presumably to indicate where the Kadee or S-Helper Service coupler is to go. I tried them and they match up perfectly. I wound up having to drill out the hole to be able to fit a coupler screw. Fairly quickly the drill finds the metal weight that is the bottom of the car. That turned out to be hard work to drill the hole deep enough for the screw, and then to tap the hole for the screw. I started off hand drilling the hole, but eventually used the slow speed setting of my electric drill to get the work done some time this century!
The next photo shows the coupler installed. I did have to file down the protrusions for this particular coupler's installation. Replacing the wheels was trivial; it's just a matter of popping out the hi-rail wheels and installing the scale wheels. I have ordered the correct trucks from S-Helper Service, which will be trivial to install once they arrive.