Hi Leigh - the V5 might only give the last 6 numbers but on your 166 engine block there should be one of the following codes in front of the V5 6 digits : - AR 36101 for a CF3 or AR 34301 for a CF2 - according to the Alfa Owner codes referenced by Gordon in this thread. This engine number is on a horizontal surface below the thermostat housing at the gearbox end of the engine.

I wish I'd photographed mine before installation as the testers will need proof of age of the engine and it's not so easy to access now! (and I dont have the V5)