Stock Ford equipment is Platinum plugs. I would stick with that.
Also the drivers side uses different plugs than the pass side due to the coil pack design.
The reason for this is due to the Wasted Spark ignition system.
Here are the part numbers you need if you want to stay stock platinum plugs.
Left side cyl 1-2-3 : AWSF-42E
Right side cyl 4-5-6 : AWSF-42EG
They are different because of again the WSI mentioned up top, so one has plat on the electrode and the other plat on the tip. This saves ford a couple cents in platinum but it adds up for those cheap ol guys.
These plugs are a direct replacment and have plat tips and electrodes and can be used on both sides. This is the most common choice and easiest.
Plat Tip and Electrode plugs: AWSF-42EE
Another choice you have is to run copper plugs which run just fine and are half the cost.
Copper Plug: AWSF-42C
I have been running NGK V-Power copper plugs in the ol nag and they run fine. I just pulled them the other day and they are in perfect condition.
Another expensive option to go by is the Motocraft Fine wire platinum plugs, but those are $5 dollars each and if you go to NGK Iridium then you spend $8 bux each.
I like my $1 dollar NGK's LOL (DOH! They rose the price to $2 dollars! [email protected]