I made a copy of this information but unfortunately I don't have a name of the person who created it.

GM baby moons 1940 thru 1955, for cost savings, used the same steel base and a same separate skin (brass?). The skin surface stamping changed as required by the design department.

"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."