I agree with brapple. get a spark plug helicoil set from the parts house. When you go to tap the hole for the helicoil, smear some wheel bearing grease on it to hold the cuttings. If it doesn't work, you'll need a cylinder head. Ford says not to helicoil aluminum heads, but I've done it before on 4.6 and 5.4 without a problem. If this happened to my vehicle, I would most certainly try a helicoil first. Can't screw it up more than it already is!
