When this thread was first posted I thought "here we go again. Same old can of worms getting opened" and I knew it would end up like this.
It's your model, do what you want.
Total accuracy is an impossible goal because I will always be able to find something out of scale on your build.
If you're building for a judged contest then go find the judge and ask them.
There, problem solved.
Now, as the worms are already out. What exactly makes for a muscle car?...