I have at last built up my 1950s Bartali race bike with mostly period-correct parts. The brakes callipers are both Universal Extra, but the front one is of a later type, and the levers may be too, though they didn’t change much over the years. The saddle is a later style Brooks B17 and I am not sure of the vintage of the Ambrosio bars and stem.
I am not overly concerned about correctness as long as the bike is in the spirit of the age. An original bike with original finish deserves to be correctly fitted out, but a bike that has been refinished and lost all its original parts should, in my opinion, be ‘in character’ rather than 100% period correct. However, it is nice to have good Campagnolo Gran Sport hubs and Sheffield Sprint pedals which were fitted to many fine Italian bikes ‘in the day’