Every part of the engine will have to be alot more heavy duty to cope with the pressure of a turbo charger. Stronger crank, rods, pistons etc. A turbo grind cam will be needed to, along with external oil cooling ie: an oil cooler, electric fan and a inline thermostat, a full-flow oil filter set-up would be a wise choice also. Don't be to keen to wind up the boost pressure to much, because if you did the expensive internals of the turbo spec motor would become externals if you get my drift........ BANG!!! :lol:
In my opinion, it would be better to build up a well thought though naturally asperated engine. It would cost the same or maybe less than a turbo motor, the advantage would be the reilablity over a turbo charged engine.
Example:
2007cc
dual twin choke Webers or Dell'orto carbs
decent camshaft, rocker shafts and push rods
a good set of cylinder heads like 044 etc
electric fuel pump with a pressuer regulator
Full-flow oil filter system a with external oil-cooler/fan with inline thermostat
4 into 1 exhaust system with something like a twin quite pack or phat boy muffler