I was looking into these rules because I was thinking about making some carbon fiber front spoilers and rear diffusers for the Dart. It would probably be more for show than go. As far as I can tell, if the car has a bolt-on bumper (like the Dart) the front spoiler can pass in front of the car since the bumper isn't integrated to the body. The "non-integrated bumper" rule I think follows more along the lines of the newer Mustangs and Camaros. Their front splitters can be pretty gnarly.

I believe the diffuser falls underneath the rear spoiler rule since it's technically not a wing. So it could go as far back as 8" behind the bumper. Or if you don't even consider it a spoiler, it's technically open to any modifications... that is till next year when SCCA throws a rule on it.