For the SFRD, They still iced with blocks even when the automatic icing machine replaced man power in Kansas City in the late 40s. They did use crushed ice to blow into the door and cover the load. This was used on loads of lettuce and other leafy vegetables. This was not usually done to citrus as it could freeze it and ruin the load. If freezing temps were to be encountered, they would actually place small heaters into the bins for the mountains and then re-ice and remove the heaters on the leeward side.
Phil