Jason
Modeling the Fort Worth & Denver of the early 1970's in N scale
The Missouri Pacific Historical Society published plans of the Muley cabeese in their Fall-Winter 2001 issue. I think they may still have some copies available. Try their website:
http://www.mopac.org/
Also, you'll occasionally find one of the Overland models on eBay, usually in the $100-$120 range.