The Ertl American Muscle stuff doesn't bring much money unless is something special or really rare. $10-$15 for the RR if you can find someone who wants it.

The Highway 61 Dart is worth a bit more, they've seen an uptick in value lately. If it's nice, unopened, and the box is good, $80-$100.

I sold most of my Highway 61 Mopar collection early this year in one lot to a guy who was planning to resell on Ebay. About 70 cars in total, I got $55 each on average selling all together and I kept all the good ones (Hemi Dart, A/FX cars, etc)