"Super GT runs GT500 and GT300 class cars, but the promotional material seems to be focusing on the GT300 class cars only."
Yeah, I know Super GT runs multi-class, but it's not a common feature in games outside of the top end sims.
Google translate (obviously not reliable) at the bottom of the 4GAMER article implies there'll 6 vehicles in 2 classes at the location test. "3 Domestic manufacturers," which is probably going to be Nissan, Honda, and Toyota.
And while it's not very conclusive evidence, all of the screenshots with a HUD show the player's position as N out of 20 places. Which is weird if you have single class race with 45 players, not so weird if you have a multi-class race.