i think you'll find his car is far from N/A..... try RB26, with some help from Race Pace
you still have stock suspension even after all the work you've done? if so, you're a brave man...
I have 290rwkw, ~560nm and no traction issues with KU36's and SydneyKid's suspension kit. SK's kit can be easily replicated with off the shelf stuff. Mainly whiteline parts but with bilstein shocks. Not ridiculous spring rates, but still firm and can handle street and track duties.
But the old bridgestones i had were not up to the task, only once i switched to the KU36's did i get full traction back.
I would start with sway bars and good tyres, and go from there.