The reason why I ask because just recently I had put in some Autolite 764 gapped at .54 and it seems like my motorcrafts (40K on them) revved and idled smoother then the 764's. I threw away my old motorcraft's and didn't get to see what the part no was. Ford dealer wants 8.00 ea. for the plugs. I know that Autozone carry Mortorcraft spark plug but for some reason they don't show a listing for our mustangs. They said maybe if I knew the part no., they might be able to look it up.