This is an engine placed on a lego toy train body (toy train snap body)

In makerware, you can rotate the top engine part if you wish to have the connectors switched. I have made this and it turned out well.

If you move the item, please note that there are 2 pieces. This allows you to change colors of the top and bottom for a dual extrusion printer.
The wheels and train cars can be found here.

http://www.thingiverse.com/thing:11671