The 300 always was a bit of a brute. Charming, sleek and handsome, but still a brute. Sort of a Klingon warbird to the Ford Starliner's feel-good Enterprise. With this in mind I started looking for alternatives to the tall, skinny 7.5" cross-plies in the kit.
I found a set of Goodyear Eagle P255/45 ZR17 tires in the parts bin. These are nice and wide, and are also a bit smaller in terms of overall diameter than the unlabeled tires in the Jo-Han kit. As a result they lower the car a bit more (about another inch at scale).
Stance and height are both good -- it all looks to be a bit of a tail-dragger which is fine. Next is to choose between mags and NASCAR steel rims. (Note the colour still comes across as slate green in the photos, although it is really more of a neutral grey.)
So: black steel rims to emphasise the brute qualities; classy mags for a brute overlaid with a charming veneer. Decisions, decisions.