Been looking at these cars for too long to remember, both N1s and Nismos, most have had AC fitted at a later date, I can only think of a handful without ac and the correct slider type climate control panel. You can tell the ac is added by the colour of the liquid line that runs over the bonnet latch panel, black line is early and probably fitted when new at the factory for a Nismo, and natural aluminium is the later type system that they possibly cost cut to save on a bit of black paint!
The Nismos will appreciate substantially, they were the car with the parts homologated so the race Group A cars could run some of the trick body and engine bits. The parts on these cars would have been very beneficial to the race cars success. The N1 was built as a race car so same same but different I guess. The Nismo had to be sold to the public as group A rules at the time dictated same as a Group A Commodore, Sierra RS500 Cosworth etc, so there 'should' be more survivors, but really they are as rare as each other as age, hard roadside objects and low class driving dictate. Hold on to your GTR special!