Moparj, for whats its worth, I'm presently working on my 318. I'm installing 302 heads with a stock bottom end, Edelbrock Performer and 750 Holley. Its running a 4spd with 3.91s. I sent this info to CompCam and told them i would most likely be installing zero deck pistons at a later date, and they recommended the XE268, which I will be installing shortly, after porting heads. Mike