What would you do? Slant performance

the hard part of some many engine builds 1. is having a blueprint and 2. a known hp and torque that you will get from it, and 3. the total associated costs of that build???? and THEN understanding what kind of seat of the pants performance you will get from that build and 4. with the other variables you have, T C, rear gears, carbtires, exhaust, etc ?????