I've been working on a model of BCR 401 for the last two days as well as a couple of other projects. Actually it's a projected I started on in 2005 but I'd shelved it while I did other things. It's a RS3 based slug, and will be unpowered but with a working DCC operated headlight.
Here's the model as she looks currently.
I made it by cutting up an Atlas RS3 frame, and rebuilding it so it's rigid but only 2/3rds the height.
The new walkway was then made by mating two rear sections of RS3 walkway like so:
I then cut up the RS3 body so it's not as tall, and replaced the sides with some new ones made from styrene and doors cut from the RS's shell