Showcase balancing

Some of the showcases seem to be misbalanced non as bad though as the muscle car track day shootout which lets you pick between the 2015 Mustang Gt 2015 Camaro Z28 and a Challenger Hellcat… So an everyday a track and a strip varient of the big 3… WTF the gt500 and gt350r are in the game would those not be more even to the caliber of muscle from the other two? The mustang 100 points lower then the challenger what gives?