You have to remember that power to weight is affecting straight line perfomance, the weight of the GT-R still counts against it in the corners, under brakes, in direction changes etc.
As for power from the S14, I'd run at a safe 210-220rwkw's if I didn't want to open the engine. I used to run mine at around 200-210 or so on track for safety's sake and it held up perfectly. With E85 you could happily go to 230 or above for little expense. You'll need computer, injectors and pump for this power, and a turbo for anything above the 210 mark, depending on who's dyno you're on as well as the condition of the engine and turbo etc