AC-R45S is the correct plug for that engine. The s is for extended tip. It is a better plug then the recest tip originally used. In the late 50,s the extended tip plug was invented & most auto makers went to them. They cannot be used on flat head engines though. The R is for resistor plugs.
George

They say money can't buy happiness. It can buy old Chevy trucks though. Same thing.
1972 Chevy c10 Cheyenne Super
In the Gallery Forum