I’m primarily an HO modeler, but I got bit by the O scale bug last year. For you purists though, I do my O scaling in three rail.
I wanted a Northern Pacific mikado, and they are only available in two rail O scale for a kings ransom ( well over $1700). So, I took another avenue and invested appx. $380.00 (on E-Bay) for a K-Line C&O USRA light Mikado, painted out the lettering, painted the cab roof, decaled it for a NP W class, and weathered it.
Here is the link to some photographs posted at the OGR forum.
http://ogaugerr.infopop.cc/eve/ubb.x?a=tpc&s=63160042&f=453102703&m=5501054591
regards,
Jerry Zeman