I’ll offer a few comments here.
First, I do not know if the Italian copies are as well built or as strong as the Winchester’s. I can’t say if the conversion is a good idea on these or not.
Second, the Winchester Single Shot, high wall variety, is a very strong action. Winchester chambered these rifles in 30-06, 303 (Savage and British), 7mm Mauser and 405WCF so it was more than a black powder era relic. These actions were even used for pressure testing ammunition (smokeless) at DuPont and Winchester for many years.
Why not find a C Sharps action or rifle for your project? They are good quality, I used one of their thick side actions for a 405WCF project a number of years ago.