I am sure it could be done, but it will be a lot of work.
It might be easier/cheaper to sell it, buy the HGT Bravo and then swap the engine for a 20V Turbo unit from a Coupe. That will be a much easier conversion, plus they are easy to tune..
There is a Turbo Bravo around these parts.
If it must be V6, the best compromise between cost/performance would be a 3.0 24v from a GTV or 166. (The 164 unit is different)
The 2.5 would be just as difficult to fit as the 3.0 and doesn't perform anywhere near as well IMO.
Giulietta 2.0JTDm (170)