How about room. You will have to place it in the tender or cut a hole and place it in the cab unless it is a diesel. The only problem is the motor coil it will have to have a feed from the center rail pass through a bridge rectifier to the coil and return to the bridge.. Other wise the engine will go in the same direction. Electronic e units are designed for DC motors. So you have to convert the old motor.
Use Lionel part # 600 0103 001.
Radio Shack Bridge 276-1146 Middle two go to the track Outer goes to the coil.