Thanks for the responses, it was very informative, thankyou.
I totally see your point with regards to the simplicity of changing the coils over, and to be honest I didn't think of that.
However, I would like to try the second more fiddly option of cam positioning.
Reason being I can use the new magneto, which is in an overall better condition, less corrosion, better bearings etc. Additionally being able to set it to the best available point of flux would be great and a good skill to learn.
I understand its just as the magnetic field begins to collapse that spark is produced. I have seen some information online but not solely for the this magneto.
Any further help on the stages of the process, disassembly etc along with ideas of cam removal would be much appreciated.