Do you mean the 500MPH mustang world or the 120MPH mustang world? A lot of sea level turbo guys I know use regular copper plugs, one range colder than factory usually to help compensate for the larger twin puffers. The feeling is they are less likely to cause pre-ignition and they're cheap enough to replace often if they foul from being too rich.
These guys spend a lot of time tweeking their air/spark/fuel maps as well, swapping different blowers, fuel pressure regulators and waste gate adjustments. They burn avgas and racing fuel mostly and don't worry about contaminating an O2 sensor with lead b/c they change those fairly often as well
Copper Autolites
I suppose as long as the engine doesn't misfire and the plug electrodes don't reach 1400F you should be fine?
One first thing I do when a boat arrives to me with misfire and/or hard start issues is change the plugs, and when it has the wrong ones the correct ones often resolve the problem.
