Looks like I'm wrong.

The 47-55 1st. Factory Assembly Manual shows the second member 2296067 for 3100 with RPO 314 Automatic Transmission. The Master Parts List (7.011, Member, Frame Cross, Second) says 2296067 for 1954-55 with HT (7.011, Member, Frame Cross, Second). However Master Parts also lists another second member 1948-53, 1/2 ton, 3686848.

"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."