I can't see the springs or perches in your video.
You state that, "The spring perches are bolted, not welded to the frame." Spring perches are normally welded to the axle.
Can you take another video, but pan out so we can see at least a complete view of one side?
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission