Your drilling the sparkplug cooling holes in the block for use with the 333's right?I would post but I better let @Don Jacks do it. they are mentioned in a long private conversation.
But basically, I will be using 333 heads instead of my current 971s on my 872 block and upgrading to Hydraulic roller lifter's combo'ed with Comp Cam Extreme Energy line that they've come out with recently that comes in at 218 in. , 224 exhaust @.050
Will have to get new everything I assume for the heads. And do a little bowl work as Don mentioned.