I know that for many years, grain was shipped in boxcars. I saw a picture on one of Dr Wayne's threads that had a boxcar modified with top loading hatches. I assume this was something done by individual roads. When would those modifications have taken place, and when did top loading gondolas come into use? I need to increase my rolling stock fleet, and I need to know what would be appropriate for grain shipments in 1949? Thanks in advance for the help.