I know this message was put up some time ago, I got insterted so i check things out my self. You can buy a power motorized chassis -Tomix tomytec. which does not cost a lot it is built for N scale. It is made in China and work very well as a part of a motorized box car. The one I made has both couple types so in can use it with repo or Knuckler couplers. I used referagotor car wich was inch and three quarters. There are several different sizes to chose from that is the length the one I use has 4 wheel drive they make others that have eight wheel drive. the big cost is shiping you can buy one for $20.00 that includes shiping. You can use any couple that you want. they come with Amoldo couplers.