Hello Big Duke6
I have been running fords since the mid 60's and NEVER had much luck with CHampion plugs in a Ford.
I think a good starting point for the gap is 35 and then you can adjust after running the motor and reading the plugs.
There are a lot of charts that will show the color of the porcelain after running.
I think 35 is a good starting gap - make sure the plug wires are run to the correct plug. You would be surprised how well
the motor may seem to run with 2 wires crossed
Best of LUck - Sam