Engine: what was said about the injection is that
direct fuel injection is not really needed. But "normal" fuel injection is still a must - don't want to be having carbs in there, do you?
In my opinion you should be looking at 1500 - 2000 hp out of the box. That would make the car the ultimate supercar. I know this sounds like much, but there's no point in having any less. 2000 sounds good
. And as you have TC and ESP, it should be reasonably easy to control.
And a couple of things about these aids. Make it so that it would be possible to disengage all of them at will (for a bit of fun), and also make TC adjustable by the driver from no wheelspin to slight to completely off.