I'd personally do 19/20 as the 18s are hideous and look like a winter wheel. If you want to track the car pick up something lighter anyway that you don't mind beating on like an Apex Arc-8R. They make 19x9.5s and up to 18x11s if you need more grip. Square setup would be a hoot. I'd go with 18s for the track but not sure how they'll look on this car. It's sort of bulky.
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