Here's a project that was nearly ruined but got saved by going prototypical. I didn't have much interest in narrow-gauge trolleys until in re-reading Cummings's book about the Concord NH system, I discovered that the trolleys to my hometown (Penacook) were 3'-gauge from the early 1890s to 1903. I picked up a Bachmann ON30 streetcar, which had the right number of windows, window shape, and overall dimensions (except that the platforms should be longer for this Briggs-built 18' prototype, but close enough IMHO). In taking it apart to paint, I broke off one of the wires to the motor brushes, then completely melted the brush housing trying to solder it back in place. So the ON30 drive was dead. HOWEVER, the Concord Street railway converted this car to standard gauge in 1903, so having an extra Lionel drive left over from another project, I installed it and now have a standard-gauge conversion. This car remained in service as standard gauge for ten years or more. The wheelbase is not quite right and the sideframes protrude a little, but it looks OK when moving.
The prototype (with narrow-gauge truck):
The model:
