What size engine do you have? If it's 4.6 or 5.0 go with Autolite platinum sparkplugs, they are high performance and a bit pricey, but I have had them in both size engines and they run the engine good and take a while before replacement.
1981 DMC DeLorean
1966 Thunderbird 390 FE HI PERF T-L (Red)
1966 Thunderbird 390 T-L (Black)
1950 Buick Special
1997 Subaru Impreza AWD