Look at the tipo plate in the engine compt to see if it's a 105.06. If so, it's a 1300, probably with single carburetor. Go to
http://www.alfaclubdc.com/Giulia1300.pdf
Fusi shows there were 12,000 105.06 built in 1964, 14,000 in 1965, 30,000 in 1966, 2,300 in 1967, etc. This appears to be the first variant of the 1300 engine in the Giulia sedan body. This is the model that was most likely the biggest seller in Italy, for price and tax reasons.
I would not call this rare, in the context of Giulia sedans, of which 500,000 total were built in a bewildering variety of models and tipo numbers, although basically there are 1300 single carb (TI, Berlina), 1300 dual carb (Super), 1600 single carb (TI, Giulia S), and 1600 dual carb (Super, TI Super) variants (plus a later diesel). On the other hand, further context is that it's a 40-year-old car of which only some hundreds are left running in the world. So what's "rare" is kinda relative.
Andrew