Ah, explains the prices you are getting quoted, I can't remember any members based in Italy before so you are probably in a very small minority. That might make the journey more interesting.
Even stock 4EFTE is a lot different to 4EFE - you might find doing the build in stages makes more financial sense and is quite satisfying in the long run.
I'm guessing you have someone willing to take on the mechanical work, although you may require a more specialized tuner for final set-up. Just on that, have you someone lined up to do the electrical work on the loom?
The mechanical side of the build is the straightforward stuff but the 4EFE ECU will crap itself once you apply boost to the equation. It's a choice between splicing bits from the 4EFTE loom into your current 4EFE one to run the 4EFTE ECU or using an aftermarket alternative to handle the boost side of things for the 4EFE ECU.
Be prepared, we are probably going to ask a hundred random questions about your car here because no-one is familiar with an Italian Toyota model