Lots of intresting pics of the two AUS Gr.A Supras on
autopics.com.au
I see in these pics that Willmington Supra had the basic cage from A-5443 (FIA Homologation Book for MA70 Turbo). TRD/TTT Japan never used a cage in this configuration for their cars ,in fact the famous car number 32 (that won the JTCC round in Sugo on Sep-20-1987 ,in the hands of Alan Jones who happen to be Australian and ex Formula One champion) is the only car I've seen having single cross Bar ,but it was build in a very different way. Based on that I'm 100% sure that Willmington car was build from a road shell.
Actually after the 1.7 rule change of Jan 1st 1988 that I have the original FIA Errata for which completely destroyed any theoretical chances for the MA70 Supra to be competitive in Group A ,I'm very surprised to see an Evolution car with single crossed cage!