The 1955 IC Freight Car Diagram book shows 24 low side (3 1/2' sides) steel gons modified for containers.
The 1960 Equipment List shows 37 steel gons with 5 foot sides equipped to carry calcium carbide in containers. AAR designation LG inside length 37'8" capacity 1672 cu ft, 140,000 pounds.
Somewhere I have a photo of one of the low side gons.
