I came up with a solution using rails and the default godot physics engine.
First, Look at the rails. This shows the rails plus the lead train, plus two carts. The focus here is the rails.
This here shows the lead train. It pulls all the cars.
This is the car. The square area is the hookup to the sphere in the rear. This is the a rear screenshot.
It's hard to set the rails in blender, but it does work. The idea is to make the train, cars and rails invisible, then have the train gfx match the cars and train.
