It’s 99.9% Original
One of the most fascinating things about the original Bullitt Mustang is its level of originality. Yes, the car is worn-out and a bit rusty. But still, it has the same paint that was applied in the Ford factory, the same seats on which McQueen sat during the chase or stunt scenes, the same engine with original performance modifications, and even the genuine holes and brackets for cameras made by the studio technicians (via Motor Trend).
However, there is one thing that is not authentic: the steering wheel. Although it’s a Shelby steering wheel and fits the car perfectly, this is not the same item McQueen held when shooting the film. The reason is simple. Someone broke into the barn during storage and stole the original one. Even though this doesn’t make this car any less astonishing and significant, it may be interesting for trivia buffs to know that somebody, somewhere, has the original one.