RacerX, I'm not BLKMGK but I'd like to put my 2 cent into that question. The SupraTT would be a could be handfull at WOT but as for normal driving it very drivable. Why, because of the turbo. You only have 650 hp when the turbo is making boost. Other wise it's a baby when there negative to 0 boost - very drivable on the rain also.
Why would it be a handfull at WOT, on the straight away the car would probably be fine but not on the twisties at high speed. The problem is the Z car was not made to handle at high speeds, not enough down force. It can be done with $$$.
As for a V8 I would thinks it's not drivable, well not as drive able as a Z with the Supra engine. Can you imagine all that hp and torque from that V8. You'll need some really fat meats on that Z. If you have a automatic, it will chirp the tires when you put it in gear. Defiantly not drivable in the rain. If the street is wet and you tap the pedal as your leaving from a dead start, you've already broke traction. I would think the same thing would apply on a stick. You feather it was light as you can and when it grabs, chirp. Too much hp and trq for a light car like a Z.
You would get a better weight balance on a V8 Z.
Again this is my $.02