I remember and article by Pat Covert I think - might have been in SAE.
But the article was about him building an AMT Nova and showing how to make it a contest car with just dealing with certain things judges look for.
If I remember right one thing he focused on was seams. You can't have any seams - such as the one on your transmission (not nit picking your model ). The only thing separating your box stock model from someone else' may come down to seam details.
I don't build for contests myself so I have plenty of seams on the parts in my models though :-) LOL