You know, if you want really accurate models, may I introduce you to my old friend O Scale?
Fer cripe sakes, these things will be whipping around in cute little coffee table layouts, not being used for an historical retrospective on the development of the diesel locomotive. The out of scale width is probably attributable to the thickness of the plastic. I know there's a GP diesel out there with brass inserts to achieve a more scale appearance, and that's very clever. But (not to sound too much like an HO scaler) who the hell can really see it without the aid of a photo enlargement?
But press on... Someone may stop rolling their eyes long enough to re-tool the whole project for you.
Lee