Hi Jean,
The CMP rear bodies were usually supplied by sub contractors to either Chevrolet or Ford, which means you could use both bodies for your C60. It's hard to see in the pictures, but I think the steel one you have there is the earlier fully welded type (there was a later type that looked identical, but was bolted), while the wood/steel composite body was a slightly later design, that was bolted and could be knocked down for shipment.
Alex