OK I have been trying to figure this out & I have succeded in confusing myself.
I have a 93 5.0 in my 66 Coupe.
I have to get some plugs & I know they have to be for the 93 motorso they willfit (different thread size) but I cannot decide what to gap them at.
The 93 5.0 should be .054.
I have a 1966 distributer (w/ Pertronix) & a carb so would that make any difference in how I would gap them.
I know the old 302's had a much smaller gap & I don't understand why the difference in the years.
Should I have a small gap .035 or a big gap .054 or something else or will it matter that much?
Advance calls for an Autolite AP25, does that sound OK?
I've made my own head hurt thinking about this!!

 

I would gap them to the same spec as the 1985 Mustang GT. It had a similar roller 5.0L engine with an electronic Duraspark II ignition and was gapped at 0.044".

Good luck!
Jeff