I have just bought an image in a workshop/dump that shows the left side with the wheels removed from what appears to be a complex rack. Possibly a horizontal bar welded to the armoured vent cover with two vertical loops attached to it in an upright position, which would space the wheels. And finally two straps or bars attaching the main horizontal bar to the fender (theses are the elements visible between the wheels in images already posted).
When the photo arrives and I can get a detailed look at it I'll post a blow up here or make a drawing to try and explain this object.
Meanwhile here are a few others that I have uncovered recently from the same workshop;