I agree, early one-piece main grille with stamped (TI) or cast (Super) center shell seems to have ended late 1967/early 1968. There was a numbering change around June 1967, from 349xxx to 859xxx series, and I used to think that's when the grille change came, but I've seen enough 859xxx cars with first-series grille to make me doubt that.
My experience is TI grilles are brass or steel, all of them chromed. Super grilles are stainless, with chromed cast center.
Well, I for sure would defer to you on early ones; we never got them much before mid 1964 here in the US, never even seen a drum brake car. But it wouldn't be typical for Alfa to make from aluminum on a "mundane" version.
The split hears were only used ORIGINALLY on S1 (1600) Supers from 65 thru MY67. Some later, like Randy's 68, were retrofitted with S1 from 5-bar/mesh grills, which were used all the way to the Nuovas in 74.
On Supers at least, can't speak to TI's, they came both ways, with and without the 4 "triangles" painted black. Period assembly line, sales brochure and car mag photos show them either way. My fairly original 65 (pics used above) are not black. A decent S1 grill I bought has black painted.
Note also the front structural element behind the heart is ALSO done both ways - painted black or body color. I prefer the former, especially on a light colored car.
That Gulia was imported to USA in 26th February 1965 to Alfa Romeo Inc, Newark USA.I guess front grille is Original,heart is not split.
According to our documentation files, the chassis number AR 454888 originally corresponds to an Alfa Romeo Giulia T.I. (105.08), manufactured on the 22nd February 1965 and sold on the 26th February 1965 to Alfa Romeo Inc, Newark USA.