Richard
It may be a repro body . As far as I know none of the original bodies survived, they were a doped canvas skin structure on a wooden frame ?
These were made on Chev Ford and Inter chassis , 30 cwt I think .
The Observers book 1972 edition has a few example pictured
http://www.awm.gov.au/collection/127736/
http://www.awm.gov.au/collection/127738/
And the AWM
Mike