Hi Andy,

How are you running your Crank sensor if you have a 164 flywheel fitted? the trigger is normally in the back of the flywheel on the 156/166 but is on the crank end on a 12v 164.
The standard flywheel swap on a 166 engine uses the solid GTA flywheel although a 2.5litre 156 one works just as well.
I had the flywheel balanced to the engine at Vibration free with the engine still in the car rather than the bare block full assembly balance that the guys with the blue printed engines have had done. Requires a bit of though but it can done! Obviously the full balance is better but if you are just running a stock engine then dialing the flywheel into the engine will suffice.
A GTA clutch can be fitted to either a GTA or a 2.5 litre flywheel. The GTA cover plate has improved clamping pressure over the standard 156 version so should be superior to a 12v version.