Pontiac Dudes comment below confirms what my engine builder did, he also filled to the bottom of the freeze plugs.
"I have filled all my blocks I use for street use. Karen's car is a 455 .060 and filled to the bottom of the outer freeze plug holes. Runs 160 and after a pass 185.
I have driven radical street engines with fill. About 10/15 degrees cooler with fill. Never had an issue with oil. Oils today never break down."
"Most builders suggest filling the block to the bottom of large freeze plug holes in the side for maximum durability in applications producing at least 600 hp."
http://www.pontiacdiy.com/how-to-imp...e-block-guide/
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 )
Old information here:
http://www.hotrod.com/articles/0712p...tiac-trans-am/
Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine)
5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension
https://www.youtube.com/watch?v=qDoJnIP3HgE