TD rings into an N/A motor would be an upgrade unless they are physically incompatible, that is being different dimensions such as TD rings being thicker or the pistons being a different size. VW didn't do that, but as far as what FIAT did, I have no idea, this is a motor that seems to have been sold in a few countries only, I think there might not be any on this continent, at all.
Parlez vous francais? You might have better luck in the French forum.