How about the Carolinas? Add a bunch of vintage NASCAR cars and the road cars on which they're based spanning from the late '40s to like the early '90s (i.e. '49 or '50 Olds 88, mid-'60s Galaxie, '70 Monte Carlo, mid-'80s Thunderbird, etc.), to the '40 Ford, Hudson Hornet, Charger Daytona and so forth they already have and have lots of unpaved backroads that were originally the domain of moonshiners for rallying.
That's a pretty great idea actually - the banked oval in the Lego expansion was a nice addition, and having a dirt equivalent to go with it would allow some fun impromptu racing, as well as giving all of the dirt roads a thematic use outside of just rallying. It'd also give PG a reason to add possibly the greatest moonshine-running car ever built - the '57 Fairlane saloon with the NASCAR homologation supercharger, the only one of which was built to order for an actual moonshine runner (who was caught before taking delivery, fortunately for the cops). 300bhp was outside the realm of even Ferrari in 1957!