I believe the 33,000 gallon, pressure tank car Walthers made a model of was around at that time.
"No soup for you!" - Yev Kassem (from Seinfeld)
Gidday, don't know how available or where you would get these from now but Atlas did make this....
http://www.atlasrr.com/HOFreight/ho33ktank1.htm#
Cheers, the Bear.
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
A couple prototype cars from Classic Freight Cars the Series Vol 2 by John Henderson, H&M Productions 1992.
LPGTankCar_zps9eb01a12 (1) by Donald Schmitt, on Flickr
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.