You can use a little bit of paint to do this. Put some wet paint on the body posts and then carefuly line up the body on the car and push down. The wet paint will transfer dots on the body where to drill. You can use a marker as well but the ink will dry much faster.

White out would work well for this as well.

I marked the body posts on the clear body first. Used a sharpie and marked the overspray film. Even if the body does not have over spray film you will be drilling out the markes or you can get sharpie off lexan with rubbing alcohol.