Good God this thread.
250bhp is around 220whp or so.
That can be daunting to make without proper cams and compression. The head also needs to be ported.
The formula for such power output isn't all that exotic, you just need to know what you're doing and research.
Pistons you select should be 4032 alloy since they don't expand as much as 2618 alloy Wiseco pistons. Mahle or Supertech (Mahle makes them for Supertech) will be more affordable and be more suitable for a street/track application that is not a crazy race built motor.
Fueling and tuning will be very important to reach these goals.