The 1st gen. Chargers where 'known' to have (rear) body lift when they hit the Nascar tracks.
A little lip-spoiler on the decklid of those models disturbed the air well enough to fill the area behind the car quicker.

The front splitter would create a low pressure area under the car and smooth out the airflow so that would helped a lot aswell I could imagine.

For that same reason I would like to mount a spoiler of some sorts on my own Dart, but will only do this after I've changed to Hotchkis-shocks and perhaps better torsion bars.

Mounted slightly higher than in the pic;