ARTA NSX (early 2003 model) 2003 TAKATA DOME NSX (late 2003 model) Regulations in GT500 are considerably looser than most GT classifications, and teams are free to change engines with other models made by the manufacturer, change the alignment of the engine, or add forced-induction systems to models which do not normally have it, however from 2010 onwards all GT500 cars run V8 engines displacing 3.4 liters. The chassis may also be heavily modified, with lightweight tube-frame "clips" being allowed in front of and behind the main cockpit, although the car must overall look similar to its road-going variant. These regulations result in cars which are possibly the fastest GT racing cars in the world.