Actually, the RX7's in those 12hr races were privately entered, built by Alan Horsley and his team in his workshop in Sydney. Since then, partly due to the success he created, Mr.Horsley has become the head of Mazda motorsport in Australia. The RX-7's were sponsored by BP in the 1992-94 events and then by local radio station 2MMM in 1995.
But the NSX was pretty heavily backed too by the Palmers, who are one of the richest families in Australia who are heavily into motorsport and co-driven by Wayne Gardner (500cc world champ, JGTC, V8 Supercars) along with the Palmers.
Also, the RULES stated that the cars were not allowed any major modifications....the most they could do was modify the airbox and removing the cat on the exhaust, the rest of it was suspension work. Same deal with all the other cars.
But that's the thing niky. They never got any handicaps or penalties over here for anything of that nature, so the car got whipped in a straight up battle.