https://en.wikipedia.org/wiki/Grand_tourer
https://www.carcoversdirect.com/car-...t-is-a-gt-car/
https://www.cars.com/articles/what-d...1420696788705/
https://ipfs.io/ipfs/QmXoypizjW3WknF...nd_tourer.html
https://jalopnik.com/5949938/understanding-gt-sports-car-racing-a-class-by-class-guide
https://www.redbull.com/us-en/gt-racing-101-a-guide-for-the-perplexed
And GT1 and GT2 in SCCA allow tube frame "silhouette" cars.
BTW, the TA2 Mustang in the pic runs in which class with the SCCA?????? Answer: GT2.

"GT badges have been tacked onto a variety of vehicles over the years, making the designation one of the oldest and most thoroughly abused in the history of automobiledom."