Spark plugs are gapped based upon the "spark energy" of the ignition, not the type of plug. Use whatever gap Ford specified for a particular ignition. Folks with aftermarket ignitions should follow the manufacturers recommendation for plug gap. People who mix and match parts are left to experiment.
Spark Plug Gaps (Ford Ignitions)
- Breaker points (1956 - 1974): 0.035"
- Breakerless Ignition (1974 - 1976): 0.044"
- Duraspark II (1977 - 1986): 0.050"
- Duraspark I (1977 - 1979): 0.060"
I can't let you get away that quickly, gotta tell at least one story. The goal of an ignition is to have a nice "fat" blue spark, strong enough to ignite the mixture in the combustion chamber, but not too strong. Yes it is possible for a spark to be so strong that it blows the fuel air molecules away from itself, rather than igniting them. Big gaps generally create "fatter" sparks, and often make more horsepower. I know drag racers that run their gaps so wide that it cooks their ignition wires. I've heard the wires sold by Ford Racing are some of the best at enduring wide gaps and resisting being cooked.