"True, if you are not concerned with the head's date casting."
Example: A mint condition unmodified 1962 Chevrolet truck with a 235 engine would have 59-62 rockers but not installed on a head with a 1956 casting date.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
