Mike, I know you CC'ed the heads and noted the similarity in size between Hemi and Poly, however I have not seen any data that supports the statement you made that stock pistons would bring you a 9:1 compression ratio. The guy who built my 270 has measured several stock engines in this family and he finds that the as-built compression is several points lower than 9:1, which matches up with offerings from other manufacturers - the quality of fuel was much worse then than it is now.

Maybe I missed something on your build - you seem to be quite knowledgeable & have the bases covered but this jumped out at me.