AC R45S or Autolite 86 gapped at .045" for electronic ign. AC R45 gapped at .035" for points. The AC R44 is hard to come by, you'd have to cross to a Champion part number. The R43 is the coldest, R44 is warmer, R45 is warmer still. Usually the second number is the heat range. Autolite 85s are cooler than 86s.... Each plug mfg has its own code for heat range, plug thread size, tip length, resistor, stock gap, etc.
