I would contact Jacobs electronics. This guy has it going on for Fords. He directed me to Autolite 45 copper cores for my '71 429 PI that runs approx. 10:1. I run and Accel 300+ ignition triggered by an Ignitor II in a recurved distributor. So he recommended gapping plugs at .045 with just the ignitor itself. I went to .050 when I installed the Accel+.
Run the coldest plug you can without fouling. That way you can run more timing without pinging. Motorcraft is a good plug to run, start with a projected tip plug 2 steps colder than what the book calls for,if you can run a non projected tip plug try them.