This group of photos was discussed here recently.
A key point is that the trucks are NOT loaded on racks, but are supported with individual wooden A-frames and blocking, the pre-rack technology. This link should take you to the original thread:
https://realstmfc.groups.io/g/main/topic/35071473?p=Created,,,20,1,0,0::recentpostdate%2Fsticky,,,20,0,60,35071473
Jack Mullen