alfas have been using guibos since the middle 1950's.
with the giuliettas (103hp or less) they hardly ever failed.
with my milano (188hp) failure can occur at 6 yr intervals (65000 miles). looking down through the engine bay (there is no bell housing since the clutch is out back), you can inspect for cracks.
my zink mk.3 running a cosworth mk.13 (155hp +/-, one guibo on each half-shaft)) used to tear them up regularly, angularity was excessive.
> jack