Rebuild 383 bottom end...

Let's start with C.C. ing the heads first.( You Tube has several threads here . Myself personally : Start with a zero decked block ,and head c.c. and head gaskets "establish quench ". There is a sweet spot ,where detonation , goes away. It's called "quench" ...and probably the key ingredient, to pump gas horsepower. This is set in stone on normally aspirated engines, carburetor style. (In my opinion )
Others ,will chime in.