The engines should easily crack the 200K mile mark. But generally the rest of the car and residual cost long kill a car as long as the maintenance happens.
The petrol engine is quite a simple one in the world if Internal combustion.
Its Naturally aspirated, ok it has 16v with DOHC and hydraulic tappets. But thats about as advanced as it gets.
It uses a standard MPI fuel system into the intake not direct which is pretty reliable as long as the injectors don't get clogged and the twin spark bit although doesn't really help anything drastic does mean if one spark fails the engine will still fire on the one good spark.
The only thing that really kills these is lack of oil (Kills bottom end bearings) lack of filter changes and if the cambelt goes.
The gearboxes are rated well over the torque values the standard engines throw out and the clutch is far stronger than needed for the torque too.
Alfa 166 2.0 Twinnie - LPG and a few trick performance parts