I agree with promoting the event but because it is such a niche market you are basically limited to the Mopar mags and sites like this to reach your target audience.
CC is already canvassing those options. Radio and TV ads are going to add only a small amount of people, most Mopar guts have it in their calender already. The rest are probably too far away for the weekend event.

When we ran with the NSCA they were all makes, as long as it was a door car. They did radio ads and didn't improve in attendence. Most of the racers brought their group and there were very few "walk ins". Ultimately gas prices put an end to my racing with them. We were taking 2-3 trucks and trailers and then a motorhome or travel trailer with another truck. We would spend $1000 in a weekend with a chance to win $250
Once people stop traveling it even hurts the local tracks attendence.