That depends on availability of turbo parts. Do you want to spend a lot of time and money buying each part you need, or just find a complete turbo motor w/ all needed parts? You can build a good flat top turbo motor, but like Ron just said:
Building a lower compression motor allows for more power at full boost... high compression allows for quicker response.
If you want a monster motor, build a flat top turbo, studs all around, metal head gasket, head and valve work, strengthened rods, hybrid turbocharger... etc etc etc. You should also read these 2 books before starting: