Passenger car into a interurban car

Maybe see if you could retrofit one of the bump trolley frames into it? Or see if there's a way to motorize an axle with some gearing and an little can motor? Cool little car, that citrus stripper looks like it worked pretty well. 

FWIW, I found this on the Bay a few years back:

Uses a Vulcan switcher chassis.  I added the pans, headlights and grab rails.

Mitch 

You might look for a Marx or RMT Budd car for two trucks, or a Marx switcher.

There's a few Standard gauge cars on the Tinplate forum you might check for pointers too.

I used Bowser streetcar and birney power units/kits/chasses for three rail O gauge railcars, gas electrics, and critters.  I don't think available still, but can be found.  You have to add an accessory reverse unit.