Typical "production casting numbers end with E used for production Engineering numbers that Manufacturing goes by. RARELY ( but it has happened) do the actual parts have the exact Parts and Service "part" number on them. Aluminum intakes are where the situation occurs the most. A few examples are C6ZZ dual four 289, C7ZX , dual four '67 GT500, C8AX tunnel port 427s , DOZX Cross Boss, D1ZX Boss 351 . "I" haven't seen a cast iron part without E as the last letter. I welcome other examples if anyone has them "other than intakes" , I have all of them