Well, I have to agree with the inconsistent quality comment, especially on the entry level models. But, it wasn't just the Italian bicycles. Just about every European marque suffered these problems, in varying degrees, due to large demand. The Japanese were the pnly entry level bicycles with consistent quality during the boom and this did a lot to establish them in the marketplace.
No doubt, there were a lot of substitution for spec'd parts during the boom, as the component manufacturers had a hard time keeping up with demand too. The Simplex does seem a strange substitute for a Valentino though, as the Simplex was spec'd on the lower De Luxe model. The De luxe and Special were spec'd almost identically, with the derailleurs and amount of chrome being the major differences. I'm thinking that your Special may have been slightly post boom, say around 1976? The boom era Special had steel rims and the aluminum Fiamme suggest something a bit later.