Chapter One: The Hellfire Club - S4-E1
New this monthContinuity mistake: Tammy Thompson's voice changes octaves as she sings the National Anthem. At the start, she's in a normal mezzo range. When the camera cuts from her to the back-and-forth dialogue between Steve, Robin, and Vickie, her voice then changes downscale to a very noticeable alto.
Chapter Two: Vecna's Curse - S4-E2
New this monthContinuity mistake: When El advances on Angela and her friends at the skating rink and wallops Angela in the face with the skate, her aim is upwards at Angela's nose for the impact. When Angela's friends sit her up in the following shot, the upper bridge of her nose between her eyes is cracked and bleeding as she screams in agony.
Chapter Two: Vecna's Curse - S4-E2
Continuity mistake: After Mike kisses El on the forehead, Jonathan is in the back grabbing his glasses from his pocket. In one shot, he's grabbing them out, and then the next shot has them at waist-level.
Chapter Five: The Nina Project - S4-E5
Continuity mistake: The seat belt keeps appearing and reappearing on Nancy's shoulder as she's driving.
Chapter Seven: The Massacre at Hawkins Lab - S4-E7
Continuity mistake: Eddie is still wearing a denim vest he took off his body and threw at Steve a few seconds earlier. When the camera cuts away and back, the vest is gone again. (00:15:19)
Continuity mistake: Eleven makes the helicopter fall from the sky and blow up some army vehicles. Within a cut, it's much earlier in the day as the sun is right above her. Prior to this, it was lower in the sky and returns that way as she and the rest of the crew are driving away.
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.