Yes, it's definitely 1982. The presence of chromed dropout flats and non-chromed stay caps is consistent with the Campione d'Italia, Campione del Mondo and Tipo Corsa frames using Columbus SL tubing which would use a 27.2 mm post. The 26.8mm post is consistent with an Columbus Aelle frame but Bianchi didn't market one in 1982, at least not in North America. The post is correct for the era, so I"d assume it is OEM, however, in the pictures, it appears to be notably pinched at the top, so the post may be too small for the frame and it may actually take a 27.2mm post. I'd also be checking inside the bottom of the fork's steerer tube for the five helical ridges indicative of Colubus SL, Finally, the headset may still be OEM, and is so, will narrow down the model.