Stock Car
Any vehicle is considered "stock" when an event promoter supplies the car in question. Regardless of the event, Race, Death Race or Arena, all "Stock" cars will be identical in all aspects such as tires, engine size, armor amounts and placement and weapon choice and placement (if applicable in the event).
The only factor that is changeable is the driver/gunners combination(s) using their skills to improve the entrants chance of being the victor in the event.