i have an 88 gt and i just replaced the heads with rebuild ones i bought from a swap meet and was told they would fit my car......they did and everything lined up until i went to pu the spark plugs back in the ones from my old heads didnt fit... went to the store and found out that all the spark plugs were the same except for 93 where they made 2 different set ups and one was a more performance head or so i was told.....any way started up the car ran great and sounded cool cuz i had no exhaust on it but i as wondering if anyone could tell me more about there so called performance ehads made in 93 i was thinking cobra

 

93 cobra motors had gt-40 heads.
not sure if they were the "p" heads.