Ah yes, South Australia, where the Tonsley Park refugees still drive Valiants and Sigmas.
The lightweight turbo cars are all pretty old (or ancient) now. Nothing wrong with racing "old" cars but unless it's a historic category it will limit your competitors. There's a whole generation of potential competitors out there who have never driven a pre-2000 road car.
And according to you, the current lightweight turbo cars are competitive outright against the big hp v8s. I don't think unrestricted turbos will make big hp v8s redundant, in fact I think they will have their work cut out for them, as they do in sports sedans. BTW, how do you think the lightweight turbos will go against the Mustang?