Should be enough here to keep you busy for awhile.
http://southern.railfan.net/shippers/shippers.html
http://southern.railfan.net/shippers/schn/schn.html
http://southern.railfan.net/flat/cars/loads/large/large.html
Yes indeed, wonderful stuff and more wide ranging than the "southern railfan" name would suggest. The Allis Chalmers stuff from West Allis WI was worth the visit all by itself.
Here is more on large open loads that should interest modelers. Keith Kohlmann can do in N scale what many would struggle to replicate in O.
http://www.bucyrus.com/media/24687/rrmc%200506%20pgs74_77.pdf
http://www.bucyrus.com/media/24690/rrmc%200406%20pgs74_83.pdf
Dave Nelson