If you are actually running Marx, you will want the Lionel 1121 switches as opposed to 1122/1122E which have guard rails that will derail the Marx(& Lionel, for that matter) engines that have large gear wheel / single reduction motors.
None of the Lionel O-27 switches are equipped for constant voltage... but can be converted like this...
The 1121 can be similarly modified, although they are not natively non-derailing, they can be made to do so for reverse loops with insulated track sections leading up to the switch or using Lionel's similar method with track trips:
