You could always just swap rearends from either of the donors that you have. That would be a farily simple swap. The front suspension from the C30 has been bolted on to the front of several trucks ranging from the early forties up. This requires some modification to the cross member and tie rod which is not that difficult. Look in the gallery at this truck he has swapped the front end of a c30 onto his original frame.
http://www.stovebolt.com/gallery/turner_ricky_1945.htmlThis doesn't look to difficult based on his picture. I would like to try it on my next project if I could finish the one I already have.
As far as the railroad wheels I am not familiar with them but I think they would look a little odd. The face of them seems too flat and I am not sure if you could cover them with any wheel covers that would hide the fact that they are rail wheels.
