The best quality plugs are the original Motorcraft Platinum plugs. People moan and say they are crap because they are a 2-piece design. That is not the case, there is nothing wrong with the design of the plug. The problem is that the GT's cylinder heads have a too smaller hole for the plug below the threads, the gap is sufficiently small enough for carbon to build up and grip the plugs lower electrode shield to the head. If the hole was bigger, there would be no problem at all.

I replaced my plugs myself. I replaced them with the original Motorcraft platinum plugs and made sure that I coated the lower electrode shield in the correct Nickel Graphite Anti-Seize Lubricant when installing them back in the car. This should alleviate any problems with removal in future.

When properly installed as above, I believe these are the very best plugs available for your car.

Cheers
Dazza