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Owner's manual suggest that you refer to the Vehicle Emission Control Information Decal on the engine radiator support for spark plug and gap specifications.
Or use the motorcraft equivalent to ASF-42P or ASF-32P
At the moment the spark jumps the gap it causes a high frequency burst of energy, this is known as RFI (radio frequency interference). This is why resistor spark plugs were introduces in the mid 1960's. Placing a resistor within the spark plug suppresses the RFI. Without resistor plugs in your car you can experience static on your radio as well as interference with other sensitive electronic equipment.
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My underhood sticker says ASF42C. The parts stores list SP450. The box has both numbers and the plug has ASF42C on it. I do not know what the other plug you mentioned is.