Judging by the shape of the rear badges, I would say it's a 1970 model year 1600 [BS]. The type of lettering is similar to the first cars and the badge on the left indicates it's a 1600. When the 1800 engine was introduced, the type of lettering changed.
Recently, i saw a red 124 Sport Spider here in my city, Curitiba. It's parked on a street and i don't lose the opportunity to see this wonderful car so close to me. I hope Fiat will make again a roadster like this. Bellissima macchina!