I think this is covered in the rules and regs section where they are talking about classifying newer cars competitively (like NASA does...)
90's models are easier, and cheaper to find then 80's models, and they need to be classed appropriately to their power and weight and such.
This car should be in ITA, regardless of it's rear drum brakes, just look at it's power to weight ratio. Not as good as some ITA cars
matt