Most with that motor---including myself---use the MotorCraft brand but the equivalent Autolite part works well too. Most who've veered from the MC or AL brand seem to experience a loss of performance and MPG's.

While I don't know for certain I once read most aftermarket plugs regardless brand name do not have the same thread profile as MC & AL, that the plug holes in the heads have a different thread profile which MAYBE contributes to blown plugs. Along with using anti-seize there might be a disagreement but in general MC or AL are the recommended plugs to use.

Check your COP boots too----they tend to give problems if cracked or worn out due age.

HTH