372or 416 and why

Hell with a closed chamber [like BB 915, old 324 318 or cracknums] you could WITH PROPER TUNE run 87 octane , like a friend of mine does, if you wanted.

It will probably be, umm lets say, 'marginal' with open chamber heads and premium octane.
Then again before any decisions made did you figure in the head gasket when cc-ing?