There is one other way to time it by ear and thats how many guys do it.

When the engine is cold and the cold timing advance/high idle is on (assuming it is working properly), there will be an extra rattle that makes it sound noisier almost like an early powerstroke. Its a louder "Clacky" sort of knock.

When the timing advance shuts off, the extra noise more or less disappears. This might get you close, but likely won't be ideal.

Go too advanced and internal damage can happen at worst, or more likely, your glow plugs will stop working. I had my truck a little too far ahead and several glow plugs stopped working over the course of a few weeks.

Make sure you have a very accurate mark on the injector pump and drive gear housing before moving anything in case you have to go back to where you had it.

Rotating the injector pump to the passenger side will advance the timing, while rotating to the driver's side will retard it.