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Do you have reason to suspect one or more of your plugs aren't working? You can do an easy test with a volt meter to see if the relay is activating. When the truck is cold and you turn on the key the voltage will drop to 10-11 volts. After a minute or two the relay will kick off and voltage will jump to the high 12's. If you don't get the lower voltage reading, then the relay is toast.
Stick with OEM's or Bosch brand. I know Autolite's are junk several have had tips break off and end up in the motor.
If you notice her getting tempermental about starting on cold mornings check the Relay voltage drop Fat mentioned and then Ohm out the GP at the valve cover gasket connector. The GP's are the 2 outside pins on each side of the connector and use the block and a ground resistance shoul dbe between 0.1 and 2.0 ohms.