The Great Race book went to some lengths to explain the radiator cowling and numerous other bits and pieces of the Goss 1986 car were 'Group C' spec and had him in trouble with the scrutineers, however what wasnt clear was that some parts and equipment were said to have flowed from TWR Europe to help Gossy along in his private entry... which apparently included a Group A shell.
At what stage the shell was at, and how many bits had to be ratted from the Group C car to make it run is something only Mr Goss can probably answer now
You can buy a 1:24 model of the Group A car at
http://www.auswidemodels.com.au/dc%201_24%20pg2.htm