Pistons and liners are usually different between turbo and natural Detroits. The compression ratio, sometimes port height, and probably where the rings are on the piston.
Head casting may or may not be the same, valve seat inserts are different, usually the valves, and sometimes springs too.
While you could just add a turbo to an N engine you'll have better long term results by starting with a real T engine, especially if you plan to work it hard.
