I'm rebuilding my 1972 302 and have found out that there is a difference between Jan thru May 1st and later 1972s. The numbers off my timing chain cover are C8AE 6059A. The numbers off my timing gear (CAM) are S408. The numbers off my Crank shaft gear is S431. The block is at the maching shop so I don't have access to the casting numbers right now. Thanks in advance.