Juan:
I agree with Bob. On my old '69 337D, I was initially told that they couldn't be overhauled. Further digging suggested otherwise, but it had to be done at the factory instead of my local magneto shop. If that's too expensive, do as Bob suggests and find a used one -- suggested sources are in the "Purchasing Parts" page of my backup Skymaster website at
www.SkymasterUS.com
BTW, you should need only
ONE magneto, the one with the RPM contacts, not two.
Ernie