I'm thinking about buying a M20J and have a question about the A3B6D
engine. Specifically, why haven't more owners switched to the dual
drive magneto of the A3B6 IO-360 instead of the more typical A3B6
engine with only a single drive magneto. Seems like easy enough to do
at the time of overhaul. Is it a cost issue (unlike core ?) ? Are
there any other issues ?