At least there’s something there to work with. I looked on Atlas’ site but there was no parts diagram. They do sell parts but no pictures or anything as far as a mount. Generally Atlas uses 2mm threaded holes. The 2 holes that are inline. If you set the Kadee box over them. Where are the holes in relation to each other and where is the coupler in relation to the cars end ? If they are the same. You might get by with the longer shank Kadee and a shim.
Looking at the design of the car. The coupler is going to have to be mounted a ways from the car body. Have you backed the car up to the height gauge to see what you might need as far as thickness for the mount which will also be used as the shim ?
Just looking at what you have. I like working with aluminum. It drills and taps easily. You can by it in strips. 1/8 is plenty thick and you can buy it in different widths. I would drill 2 holes to match the 2 in the Atlas chassis. Trim it to fit. Then figure out where to mount the Kadee. Drill and tap your holes. You may still need the longer shanked version seeing this is a 60 ft. car. I’ve made mounts for a lot of conversions. Just not this particular car. I can give ideas. But without the car in front of me it’s hard to tell you what will work.
