Steve a good start would be the series of 46 articles that Ted Cullotta published in Railroad Model Craftsman, titled “Essential Freight Cars” http://steamerafreightcars.com/prototype/research/EssentialFreightCars.html

While many of the models are resin, this list certainly provides a list of important models that have already been offered in HO.

Doug Harding

www.iowacentralrr.org