I thought I'd update this for future Searchers. Installing Harmonic Balancer on M103.

This is the process I followed:

Drain Radiator.

Remove Fan shroud.

Disconect Radiator hoses, trans cooler hoses.

Remove Radiator.

Remove Aircon.

Remove fan and pully. Use the small hole in back to lock, or a pair of vise grips. (Later for me)

Clean up crank nose - used a small box file to remove burrs on the key way. It was burred where the old key have broken and spun. Luckily the damage was minor.

Checked that key was a tight fit, there was no play, but it would fall out.

Replace Main seal. Pry the old one out with a screwdriver. Install a new one using a block off wood with a hole in the centre for the crank to pop through. Tap the seal in.

Place the Key in the slot.

Start sliding the hub over the key. The key will try and push out the back.

Once the hub is half way over the key, tap on with a block off wood. Its a damn tight fit.

Put main crank bolt in to hold hub on. 300NM is the value used to tighten. From what I have found out the bolt isn't a stretch bolt. I reused and have has no issues after several hours of running.

I locked the crank by using a 3 mm rod through the teeth in the ring gear at the torque converter.

I inserted and used a jack to hold it against the ring gear.

Bolt balancer to hub.

Bolt pulley to balancer.

Replace Fan pulley, fan.

Replace fan belt.

Install Aircon.

Install Radiator.

Install Shroud.

Fill Radiator.