Why the class distinctions?

I've always wondered, why are the supras and Skylines (now Z cars) classed in GT500, while the 996's and Modenas in GT300? I've always thought the euro cars had much more horsepower.

It may be just a question of cost... Making a 911 or Modena upgrade to 500 hp (as they're initialy around 400...) costs more than just let their engine deliver the 300 hp needed by this class... Fiability is obtained more easily too. And competitivity costs much less! Something important for private teams!

Just have a look at the GT500 class, you'll see the cars have few things in common with the road model they're coming from: CF everywhere, bodyshape completely remodeled... While GT300 remains closer to the road cars.
When you see how competitive the Murcielago and Maranello are in Europe, and how difficult it is for them to be competitive in GT500, you can understand easily that it would be impossible mission for Modenas and Carreras!!!

... And honestly, I wonder if gt500 are really 500hp and gt300 really 300hp... (I feel 100hp could be added to match the truth...)

the GT500 class is for high dollar supporting manufacted teams, the GT300 is a class for people with less money that want to participate, cars that come with more power stock dont mean shit