This chassis is designed to fit powered bogies.  See below for link
 
Each of the parts for the running Rail Motor are offered as separate items:
 
Chassis & motor spacer
Main body Shell
Windows
 
Body shell and chassis come unpainted
 
Powered and unpowered bogies to fit the chassis available from
Petey's Printed Parts  www.ebay.com.au/itm/257232708328
 
There are a number of tiny holes printed into the cross braces of the chassis.  This is to thread the wiring keeping it below the windows and neat and tidy inside.