Spark plug advice

Heat range is a '5' in NGK for your engine. Rarely is there a need to change that, & not in this case.

If you want to run bigger plug gaps, use Plat or Irid plugs. The smaller centre electrode requires LESS arc over voltage & is therefore less likely to misfire. Use 0.060" gaps or more. Another Plat & Irid advantage: they are very hard metals. The electrodes therefore stay sharper over time in the engine. Nickel/steel elecrodes in conventional plugs are softer & will round off from spark erosion. The rounded electrode requires more spark voltage & can lead to misfires.
Others will reply to this & say you do not need 0.060" gaps. They have yet to explain how we evolved from 0.010" gaps of magneto ign in 1915, to, over the years, 0.080" gaps. [ some GM engines ran 0.080" gaps from the factory; they could have run 040....but didn't ]. Getting bigger....not smaller.