Seriously, what is it, 250kw, 400kw, or 1000 Flywheel HP? - There are massive differences in these setups.
If you intend to be able to produce 1000 HP down the line, then you need to build the motor correctly now, or be prepared to build it again later. I would suggest sourcing an N1 block as the base if you are *really* going to be chasing such HP levels.
There are a number of areas you haven't mentioned yet that are going to need attention
- Injectors & Fuel system?
- Camshafts?
- Sump/baffle setup
- Headwork?
Basically, for anyone to properly advise you of what you do and don't need, you need to more accurately identify what power you are going to chase from the get go