Tom,
This is a quote from TA Bob "All of the water cross overs will be blocked on the out board side of the head surface. The builders will transfer the holes that best meet the holes in the head being used."
I guess I took that as they would be cast, shut. I also had a conversation with Rob that if they were 5/16 that they could be opened further or plugged easily. So now I'm not sure.
What I can tell you is that mine were a PITA to plug as some were overlapping and required a very large hole to cover completely. I spent a weekend with a magnetic drill, a large selection of resharped end mills to find tap drill sizes, and pipe plugs
__________________
Wade Congdon
BOP Engineering
Hi-Performance Specialty Parts for Buick, Olds, and Pontiac
www.bopengineering.com