Either way, that appears to be an AC/DC motor. The simplest thing is to stick a two dollar bridge rectifier in there, and run it on DC.
The only reason Lionel and 3-rail is still AC is tradition. Most motors are now DC, so converting the transformer to DC could be done once at the transformer, or multiple times at each locomotive. If you do it at the locomotive, you also need a complicated E-unit. Makes no technical sense.
