Brian, the well-modified Porsche 911SC that I used to take to the track had twin plugs/twin coils/twin ignition sources though not mags--a modification that I made to the engine--and it was solely for the purpose of allowing a substantial compression ratio on what were comparatively wide combustion chambers (the engine was also upgraded from 3.0 liters to nearly 3.4) without risking detonation. I needed to be able to light off flame fronts from two sides of the combustion chamber, not just one.
And after all, a 911 engine is just a roadworthy light-airplane engine...