On one hand, it is hard to answer this question in the absence of a published diagram of the VJ4 BR35 advance curve. The Giulia Sprint Speciale/Spider Veloce were about the most highly tuned Alfas from that period. To get an abolutely identical curve, you would have to take your distributor to a shop that still has an ancient distributor test bench and have them plot the curve. Then you would purchase the programmable 123 and input the curve as measured.
On the other hand, these vintage distributors were all set for octane ratings that are no longer available. Since many of the pre-programmed curves are intended for Alfa twin cams with twin Webers, and the curves were not wildly different to start with, I believe the 4-R could be set to work decently on your car.
Why do you want to replace it?
If you do, make sure you match it with a lower primary resistance coil to fully benefit from the electronic triggering. This will allow you to increase spark energy, along with an increased plug gap. Aim for a 1.5 - 2 ohm primary resistance such as the Bosch "Red " coil.
On the other hand, these vintage distributors were all set for octane ratings that are no longer available. Since many of the pre-programmed curves are intended for Alfa twin cams with twin Webers, and the curves were not wildly different to start with, I believe the 4-R could be set to work decently on your car.
Why do you want to replace it?
If you do, make sure you match it with a lower primary resistance coil to fully benefit from the electronic triggering. This will allow you to increase spark energy, along with an increased plug gap. Aim for a 1.5 - 2 ohm primary resistance such as the Bosch "Red " coil.