Hello I will help you with your question,
I think you are going to replace the entire distributor assembly. What you are calling the "magneto" I call the reluctor and it should be firmly fixed to the distributor shaft. The tips of the reluctor should align with the pickup coil when the rotor is at the #1 TDC position.
See if the procedure below sheds any light on where the problem is
Let me know how I can help you