Here's a quick link to the finished models (HO scale):
There are no commercially available models to match these cars, but an E&C Shops 50-foot PS boxcar kit (also marketed for Branchline Trains) was used as the basis of a kitbashing project.
Here's a draft of the modeling article:
I haven't attempted this project (yet... but Craig certainly has!) -- I would appreciate any comments that could help clarify or expand on it. Thanks.