I have the opportunity of a plastic 400 with a bad body, but the motor seems intact. From your response, the 400 motor would be the better fit, to wedge into the 1588 shell, that I have. Since our conversations with the 1588, I was able to obtain two complete running 1588 locos, and have since added the freight cars, and passenger cars, that would comprise the Lionel Outfits 1548 & 1549. I would like to work on the 1588 shell, and fit a Marx motor into it.
Of course, I have another problem with the another Lionel Windup. I have the 1511 Commodore, with (You guessed it!!), bad motor. They winding mechanism doesn't lock, when wound up. I haven't got a clue, as to how to remedy the problem, and the design of the body wouldn't be able to substitute a Marx motor, in place. I just keep searching for a Lionel 1511 or 1508, that may be found cheap enough. Thanks for the reply on the 400 motor.
