Links 1, 3, and 4 seem to have changed since they were posted. Number 1 might have changed to:
http://www.goo-net.com/usedcar/spread/g ... 88014.htmlIf you are looking for a genuine GTR, the English speaking world does not seem to have an absolute method to solidly determine if a car is a GTR or a GT that has been converted with GTR parts. The Japanese do not seem to want to tell us. So if the goal is to have one of the few, rare, exclusive, genuine cars, the best advice is to assume all cars are GTs that have been converted and challenge the seller to prove that the car was originally a GTR.
Link 1 has the white firewall as you mention. It is missing the regular grille emblem. It does have the black mirror backs and antenna base. The dash panels are black instead of wood (correct), and the trunk hinges are body color. The blacked out tailgate looks correct and ends above the bumper. The side stripe is wrong in angle and size at the rear wheel arch and quarter panel. The car has had a very extensive restoration, which may account for some irregularities.
Link 3 lacks the DOHC grille badge, has wood grain dash panels instead of black, chrome back mirrors and antenna, copper color valve cover, and the tailgate black out extends too low behind the bumper. But the side stripe looks correct.
Neither car has black paint between the cowl and the top of the fire wall, behind the hood latch, wiper motor, and where the chassis number is printed. The color pictures I have of cars believed to be genuine have black paint in this area. The B&W period photos do not show enough color detail to be sure.
If you are looking for a good, solid car, and not worrying if it was one of the rare ones, then inspect it like any car for mechanical and structural soundness.
Most of the disagreement seems to be if a car is genuine or not, and if it demands the highest of prices. I don;t know if there is as much disagreement that a GT converted with GTR parts would logically deserve a price somewhere between the price of a GT and the premium price of a genuine GTR. After all, lowly GT restoration parts are rare and expensive enough as it is. The parts to convert a car would have to come from stripping a genuine car, transplanting engine and transmission parts from an equally rare 117 Coupe or Gemini ZZ/R, or some of the few GTR parts that were sold by the Isuzu parts department in Japan. Theoretically, unless there is some plentiful source for G161W engines, a converted car might be more rare than a genuine car.
Just to make it absolutely clear, my opinion is we do not have a good ID method until we know the "small detail / little spot" that the Japanese experts know and don't seem to want to share. I'd pay to see someone walk onto a couple used car lots and demand the seller prove a car's authenticity just to see what the reaction is.