Denso Iridiums?

[84LX89GT]

It never hurts to try different brands/gaps on your spark plugs. I usually just use Motorcraft coppers because i've never had a ford run bad on their recommended plugs because of them. I don't think you'd gain much if anything by going with those plugs. One trick i've heard of is filing down the ground electrode so that instead of hanging over the center electrode, the end of it stops at the middle of the middle of the center electrode (looking "top" view at the electrodes). This supposedly unshrouds the spark kernal exposing it to more air/fuel (the idea behind split fire plugs). You can also "index" spark plugs and line them up toward the intake valve or exhaust valve (or anywhere in between) and see if you get some gains by having all the plugs lined up equally toward an area of the combustion chamber that you choose.