I think your model might be a little too low in the polygon department. There isn't a lot of detailing on the styling either, which kinda makes it a little, late 80's. Here let me show you what I mean by detailing. In more modern muscle cars, they give the impression of a very tough looking thing. Look at the rear fender. Look at how it archs upwards. Those fenders aren't even going outward on the Chrysler. The lines are only up going up. It's like looking at a particularly strong horse's rear legs. Almost like it's some kind of pony. The pillar doesn't stop at the top of the windshield, it flows back with its thickness to the back, where it's roof line ends at the middle of the rear wheel well area. Also more rounded off at the top. And look at the sides of the rear bumper. They curve up and inward, assisting at giving that figure. The thickness (and tallness) of the rear is there too because of those lines. And look at how deep those tail lights go in! Also duck lip. The front is got some stuff going on too on the bumper. Notice how the bottom part of the car curves inward. Many, if not all muscle cars do that. It is what helps assist that figure in the back. Check out how deep in those headlights go in the grill. It looks serious. The hood curves towards it closer to the end of it too. There are similar styling cues on the Camaro as well. The rear fender has the same effect as the challenger, but its different. there isn't a flowing line to show that "strength" look. There is a parallel line from the rear side windows to the rear of the car that shows that strength look. The lower middle part of the door has that indentation thingy to help highlight the aggressive arching of the rear. The pillar is pretty thick too. Also, it looks like it's squinting, like you slept with its wife when he was gone at work. And he finds out the hard way. When you model, you have to notice styling cues that make up what it represents. Without any, a car would look like this. You probably should do more than "a little tweaking" on your model before you have put it in-game first.
