I need to repair a U36B auto-train with the older 8 wheel drive chassis - the heavy one. I'm finding a lot of U36B and GP40 (same chassis) locomotives on e-bay but rarely does the seller show the engine with the shell off or even the bottom of the locomotive so I'm not able to identify the chassis I need to salvage parts. Is there a way to identify the type of motor/chassis from the box number, if it's the original box, or engine number on the side of the cab or some other way?