That was a good question Donny.
One thing that should be considered is that you have no idea what you will prefer to do with the car until it's done. If you are looking for justification of your ideals, I'm the wrong guy.
I'd rather tell you my honest opinion since I have the experience.
If you just want to show up to a road course/autocross and have a good time and aren't serious about competing and honing your skills, I think it's ok. It will be a short duration car. I just don't see you cooling efficiently enough to make many laps. I also think it will prove difficult to drive in any handling segment. Specifically due to the massive amount of power and the unpredictability of turbos. Racing is a delicate dance of being right at the edge and that means feel is crucial. Having all that weight is going to make it push worse than most. I'd shoot for a 295-315 with the proper rim size. With a DSE sub that means adding the wheel width to the outside of the rim to prevent control arm/frame rub. That will require fender mods.
You have to remember that you are not GM, you don't have millions for R&D. You need to error on the side of caution if you want a predictable and reliable car. Having that much power will be a handicap for pro touring.
A mild supercharger would be a better option due to less heat. They just aren't as pretty and I get that. If I was going to spend that type of coin, I'd have Stielows engine builder build you an LS9. It would be all the power you will ever need and it's been done.