I have a collection of 3-rail New York Central (P-2b and S-2) and New Haven (EP-3, EF-3, EF-4, EP-5 and FL-9) electric motors by MTH, Lionel and Sunset. All would be realistic to run on outside 3rd rail. The idea intrigues me but it would be a huge effort to convert them and build a layout. Very interesting thread though.
MELGAR