I spent years reading and talking to people who had done it before I built mine.
Math. Compressor maps. Being realistic about a big heavy street car, my fabrication abilities, and what I wanted to spend.
Originally used ford 2.3 manual units on my 383. Similar to a 2.5 with the Mitsubishi turbo on it. Now some stage 5 PTE's that feel more like the Garrett on 2.2, for those that played with those cars.
Totally different animal than the volare and ugly car tho