Before the car accident, the vehicle had roll down windows. After the car accident, the vehicle had power windows.
When Redfield is driving out of town for the first time, it's obvious that there is no dog in the car with him as the car makes the turn onto the main road and crashes into the invisible barrier.
In addition to what has already been mentioned, other differences between the wrecked and unwrecked Impalas are the side view mirrors are of a different style/mounting location and the front license plate is missing after the accident and it is not lying on the ground as if it had fallen off.
When Philip Redfield first pulls into the gas station, he gets out and opens the radiator cap to check the water level. Opening the cap on a car that has just been driven causes hot water to rush out, but this didn't happen. Also the cap itself would have been burning hot.
The scene where the car crashes into the invisible barrier: a frontal shot shows the vehicle has sustained considerable damage. These particular older cars were unsafe compared to later models, with hard metal dash and fixed projections such as mirror and control switches. There were also no airbags or crumple zones designed into the bodywork. The unrestrained driver of this vehicle would have impacted the dash due to bodily inertia and been, in all probability, very badly hurt.
When Philip runs face first into the wall outside his house, his cigarette doesn't crumple.
When Redfield punches Evans in the jaw, his fist never touches him.
After the accident into the invisible barrier, the front of the wrecked Impala is not flattened as if it hit a vertical surface, but has irregular damage as if it struck an irregular-shaped object like another vehicle.
The car driven by the main character, Philip Redfield, is a 1959 Chevrolet Impala, but the hub caps say Pontiac.
When Redfield pulls up at the sign for the town, a crew member, moving up and down, is reflected in the car window.
With a population of 981, Pleasant Valley might have a minimum viable population if inbreeding were not considered, but in reality, it has only about 25% of a minimum viable population.