Hi
I replaced all the bulbs in the dash of my Beta with LEDs including the alternator one, the brightness is not a problem. The only issue was the variable resistor/rheostat to dim the display which in may case was actually wired out and MIA. So I purchased a 500 ohm one to replace it which is now acceptable though does not fully dim the lamps, so maybe a 1k ohm would have been better. No idea on the Fulvia how this resistor is integrated into the dash, so changing it may not be practical?
Peter