I think the PWC version had a can motor, and they gave the folks who preordered it an extra freight car to make them feel better about the change in specs.
Somehow, the very last version -- Conventional Classics? -- reverted to an AC motor, albeit one made in China whose parts are not interchangeable with Postwar or MPC. The sku is 6-38340 but it's often referred to as set 1587S.
I would love to know more about the conventional classics version... How did it run? What are the differences between the "Chinese" pullmor motor, and the original?? Honestly, before I paid big bucks for any of these, I would be tempted to find a 2037 in good condition and just paint the darn thing pink!