i just got my new head in and the casting number is different from the one that was on the car. i know there was two heads for the ld9 but the number on the car does not match the two made for the car. the car had a casting number of 24574683 the new head has a casting number of 24574683-18. whats going on here??? i double checked with the FAQ and and the head that was on the car in not in there.