Chapter Five: The Flayed - S3-E5
Continuity mistake: When Hopper is taking Todd's car at the gas station he hands Todd a Slim Jim he was eating, then they pan away from them to show Joyce Byers and Hop talking. When the scene widens Hop has the Slim Jim back in his hand and hands it to Todd again. (00:24:25)
Chapter Five: The Flayed - S3-E5
Continuity mistake: While Hopper lies his way into stealing the car from Todd and claims that Alexei has murdered many children, Hopper pushes the driver seat back into its proper upright position. Then as Hopper introduces Detective Byers to Todd, the driver seat is once again leaning toward the steering wheel before being upright in the next shot. (00:24:30)
Chapter Five: The Flayed - S3-E5
Continuity mistake: In the woods, when Alexei is running with Hopper chasing after him, the individual shots of each of them running are flipped. Note Alexei's shirt pocket and Hopper's bloody head wound. (00:22:30)
Chapter Five: The Flayed - S3-E5
Continuity mistake: When Robin takes the chemical container off Erica, in the shot of Erica saying "It could be useful", Robin is holding the container upright. In the next shot, it is being held at a rotated angle, then upright in the following shot. Two shots after that, the container is suddenly rotated again, then back to upright when the shot cuts. (00:17:25)
Chapter Five: The Flayed - S3-E5
Continuity mistake: Eleven and Mike are sitting next to each other at the hospital. Eleven looks to her left in one shot and the camera changes angles. She's now looking straight ahead and immediately looks to the left again.
Answer: They're both muscle cars, but that's about the extent of the similarities. But the 70's were filled with a lot of muscle cars, so some car models may look a bit like another's. Billy's car is a late 70's Chevy Camaro (probably a ‘79). Mad Max's car is a 1973 Ford Falcon XB GT. Incidentally, the Ford Falcon was produced by Ford Australia and wasn't an American car, or even sold in America (as in not sold at dealerships).
Bishop73
According to the experts its a Camaro '78 with added vented side fenders.