Well you are all wrong!!
There are actually 2 cars.
The white one is the original (as in first) car and is fitted with the 186X engine.
The silver car was an updated version and is fitted with a 202 engine.
Cheers,
JPXU1 
Don't believe everything you read on wiki.
"One of the prototype GTR-X cars has been recently restored back to its original white paint finish and remains on public display at the Salmon Street offices of Holden in Melbourne, Victoria. Another, is located in the National Motor Museum in Birdwood, South Australia."
Hopefully, it will soon read like this:
The only existing complete prototype GTR-X car has been recently restored back to its original white paint finish and remains on public display at the Salmon Street offices of [[Holden]] in [[Melbourne, Victoria]]. This car, originally white as pictured, was painted silver in the mid 70's. It had UC Torana SL/E wheels fitted and a couple of other cosmetic changes (bonnet badge etc) in an attempt by Holden to move the car with the times and "restore it". During this period it toured motor museums inc. The Birdwood museum in S.A. In 2003 the car was returned to it's original build condition (white) by Car Shine in Melbourne, prior to being shipped to the US to the General Motors Technical Centre at Michigan for the celebration of automotive design spanning the past 75 years.
http://en.wikipedia.org/wiki/Holden_Torana
Edited by rodomo, 26 December 2010 - 10:27 PM.