The GNX was factory equipped with every available option of a fully-loaded Grand National, with the exception of T-tops or a sun/moonroof because these could compromise the structural rigidity necessary in a high-horsepower performance vehicle with such body-twisting torque. However, by special arrangement (usually at the behest of influential first owners), several were retrofitted with roof options by ASC. In the GNX cockpit, the stock dash cluster was completely replaced with full instrumentation featuring a custom Stewart Warner analog gauge package. The instruments included a 160 mph speedometer, 8,000 rpm tachometer, turbo boost gauge, oil pressure gauge, fuel gauge, and water temperature gauge to properly monitor the car's vital signs.
Each GNX received a special numbered plaque mounted on the passenger side dash which identified the build number of that particular vehicle: 001 to 547.